Kiev, Ukraine (CNN) -- Western powers increased pressure on Russia Wednesday to talk to the interim government in Kiev in a bid to ease tensions over Russia's military intervention in Ukraine's Crimea region.
Russia has been warned that, unless progress is made toward ending the high-stakes showdown, sanctions may be on the agenda when European Union leaders meet Thursday in Brussels, Belgium.
But the impact of sanctions, if they were imposed, might be felt by other countries, too. In a tit-for-tat move, Russian lawmakers are drafting a law that would allow Russia to confiscate assets belonging to U.S. and European companies if sanctions are slapped on Moscow, Russian state media reported.
The Russian threat was not specific, but numerous large European and U.S. companies have interests in the region and Russia is a major supplier of gas to Europe.
The maneuvers came as world leaders met in Paris for talks that were originally intended to focus on Lebanon, but wound up including discussions about Ukraine, too.
Russian forces remain in effective control of Crimea, a Black Sea peninsula of Ukraine that is home to a large Russian naval base, in a standoff with Ukrainian forces loyal to the new, interim government in Kiev.
U.S. Secretary of State John Kerry and his Russian counterpart, Sergey Lavrov, met three times Wednesday at a meeting of foreign ministers in Paris. They greeted each other cordially at the Russian Embassy, according to the pool reporter traveling with Kerry.
Kerry urged direct talks between Russia and Ukraine, the official said.
One of those meetings included a "brief and informal discussion" among Kerry, Lavrov, Britain's William Hague, France's Laurent Fabius and German Foreign Minister Frank-Walter Steinmeier, the official said.
What happens at the EU meeting on sanctions "will be partly determined by Russia's willingness to sit down with Ukraine," Hague said.
If no progress can be made on de-escalating the situation, then there will be "costs and consequences," Hague said.
Kerry: Clear legal obligations at stake
Hague's comments came after he, Kerry and Ukrainian Acting Foreign Minister Andrii Deshchytsia discussed their next steps and before Lavrov arrived in Paris.
Kerry reminded Moscow that it had, like Washington and London, signed an agreement in 1994 -- when Ukraine agreed to give up its nuclear weapons -- "to refrain from the threat or use of force against the territorial integrity or political independence of Ukraine."
There are "very clear legal obligations that are at risk in this," Kerry said.
Deshchytsia said he hoped for bilateral and multilateral consultations with Russia.
At issue is Russia's insistence that the new, acting government in Ukraine is not legitimate.
Western powers argue that ousted President Viktor Yanukovych fled the country, leaving a void that had to be filled. They point out that the interim government was voted in by a large majority of parliament, including members of Yanukovych's Party of Regions.
In a joint statement after their meeting, the United States, the United Kingdom and Ukraine called for international observers to be deployed to Ukraine.
This, they said, "would help address any concerns regarding irregular forces, military activity and the treatment of all Ukrainians irrespective of their ethnicity or spoken language."
Russia has cited a putative threat to ethnic Russians in Ukraine as a justification for military intervention in the country.
The Organization for Security and Co-Operation in Europe, a regional security bloc, said Wednesday it was sending 35 unarmed military observers to Ukraine in response to a request from Kiev.Lavrov said earlier Wednesday that decisions on whether international observers should be sent into Ukraine are for leaders in the country to make.
Putin vs. Obama: facing off over facts in Ukraine
France: Invasion violates international law
On Tuesday, Russian President Vladimir Putin denied Russian troops were in Crimea, but said he was reserving the right to take military action to protect the safety of Russian-speakers in eastern Ukraine.
He slammed the interim government, which replaced Yanukovych, a Russian ally, as illegitimate.
Fabius, the French foreign minister, set out a different point of view Wednesday as he declared that sanctions could be in the cards.
"The invasion of one country into another is contrary to all international laws," Fabius said via Twitter. "We must return to dialogue and to bear in mind that Ukraine should work with Russia and the EU."
On Tuesday, Kerry accused Russia of making up reasons for intervention in Ukraine, saying "not a single piece of credible evidence supports any one of these claims."
NATO members were set to meet with Russia's ambassador to the alliance Wednesday amid concerns the crisis could spread beyond Ukraine.
And NATO Secretary General Anders Fogh Rasmussen and Ukrainian Acting Prime Minister Arseniy Yatsenyuk are due to meet Thursday.
EU Commission President Jose Manuel Barroso announced Wednesday in Brussels that the EU would offer an aid package worth $15 billion (11 billion euros) to Ukraine. He said the package was "designed to assist a committed, inclusive and reforms-oriented" Ukrainian government.
Barroso said on Twitter that the aid package would consist "of immediate short and medium term measures offering trade, economic, technical and financial assistance to #Ukraine."
During his visit to Kiev on Tuesday, Kerry announced the United States will give Ukraine's interim government $1 billion in loan guarantees. Senior U.S. administration officials told CNN the move would help insulate the Ukrainian economy from the effects of reduced energy subsidies from Russia.
Ukrainian authorities have said they will need $35 billion by the end of 2015 to keep their struggling economy afloat.
Meanwhile, the EU said it had acted to freeze what it suspects are misappropriated Ukrainian state funds held in Europe by 18 people whom it did not identify.
German Chancellor Angela Merkel is trying to construct what a senior U.S. administration official characterized as an "off-ramp," or way out, for Putin by putting international observers in Crimea to ensure ethnic Russians' rights aren't violated.
U.S. President Barack Obama floated this idea in a call Saturday with Putin, and Obama and Merkel talked about it Tuesday.
In Crimea: 'I feel unsure about what will be tomorrow'
Lavrov: Military coup in Ukraine
Lavrov, speaking Wednesday morning in Madrid, Spain, showed no signs of retreating from the position taken Tuesday by Putin.
The Russian foreign minister said the crisis had begun when the international community failed to react to the anti-government protests that preceded Yanukovych's ouster.
"There was a military coup, and the legitimate president was removed by methods which were not in the constitution or legislation," Lavrov said. "If we are so lenient to the people who are trying to govern our neighbor, everyone must realize a bad example can be spread and there shouldn't be any double standards."
Lavrov restated Putin's denial that the troops who control Crimea are Russian, saying the troops in question are "self-defense" forces over whom Russia has no control.
"This problem is multifaceted," he said. "In order to calm the situation down everyone must act in accordance with the law."
Moscow wants an agreement that was signed February 21 between the government of the ousted Yanukovych and the opposition to be the basis of any settlement. It promised new elections, constitutional reforms and the disbanding of illegal armed groups.
State-funded network's news anchor: 'What Russia did is wrong'
Fears of instability
Meanwhile, tensions on the ground mounted.
Robert Serry, the U.N. envoy to Ukraine, was threatened by armed men who wanted him to get into a car, U.N. Deputy Secretary-General Jan Eliasson told reporters Wednesday. The United Nations expects local authorities to provide protection for Serry to return to his hotel from a cafe where he had stayed put, Eliasson said. CNN affiliate ITV reported that Serry had agreed to leave Ukraine immediately.
In the eastern Ukrainian city of Donetsk, protestors took over a local government building and were seen heading to the local treasury, witnesses told CNN Wednesday. The protesters were calling for a referendum on the status of the Donetsk region and said they want to see the region gain more autonomy.
But no violence has erupted in Crimea, where Russian troops control military bases and key installations.
Andriy Parubiy, secretary of Ukraine's Security and Defense Council, told reporters in Kiev Wednesday that the situation in Crimea was calmer than it had been Tuesday.
Parubiy said Russian forces had made no new military gains on the peninsula but warned of the danger of new attempts by pro-Russian protesters to take over government buildings in eastern and southern Ukraine.
Warning shots were fired Tuesday by the Russia side during a confrontation with Ukrainian forces at a military base near the port of Sevastopol before the situation was defused.
Col. Sergei Astakhov, assistant to the chief of the Ukrainian Border Service, told CNN its officers have increased security checks at the Russian border, particularly in the southeast.
During the prior day, he said, they turned back more than 300 people seeking to enter from Russia whom they suspected of participation in disturbances.
On Tuesday, Putin said he had ordered Russian troops back to their bases after they participated in military exercises near the border, a move that some observers saw as a positive sign.