BRUSSELS — European Union leaders called a special summit for Thursday, at which they are expected to suspend talks with Russia on economic cooperation and liberalized visa rules if Moscow hasn’t taken steps to calm the crisis in Ukraine’s Crimean peninsula.
There has also been discussion of halting imports of Russian natural gas to Europe, although no decisions have been made on taking such a drastic step.
The European Union is by far the biggest consumer of Russian gas, and any disruption would come at huge financial cost to Moscow.
EU foreign ministers have also joined the United States in stopping preparation for the G8 summit, which is set for June in the Russian resort of Sochi.
Catherine Ashton, the EU foreign policy chief, said the alliance would give Russia until Thursday to show clear signs of good will, including a willingness to open talks and a withdrawal of Russian troops to their barracks in the Crimea.
‘‘The ambition is to see the situation improve. If it doesn’t, then the course is set,’’ Ashton said after the foreign ministers’ meeting.
She said she will meet Foreign Minister Sergei Lavrov of Russia on Tuesday in Madrid.
The ambassadors of NATO’s 28 member nations will hold a second emergency meeting on Ukraine Tuesday after Poland invoked an article calling for consultations when a nation sees its ‘‘territorial integrity, political independence or security threatened,’’ the alliance said in a statement.
At the EU meeting, many foreign ministers stressed that the immediate focus should be on diplomacy and promoting direct dialogue between Russia and the new leadership in Ukraine.
The EU is Russia’s biggest trading partner, and Russia is the EU’s third-largest partner.
Russia is the largest exporter of oil, gas, uranium, and coal to the EU.
Economic sanctions would hurt all sides, said Foreign Minister Frans Timmermans of the Netherlands.
‘‘Those consequences will be bad for everyone, but for Russia they will be far worse than for the EU. We can target other markets if we have to. [Russia] will have trouble to quickly find other customers,’’ Timmermans said.
The developments in Ukraine frightened investors around the world Monday, sending stock indexes lower and energy and staple foods higher.
Even if military conflict does not break out, Western powers are looking at how they can punish Russia for what they consider to be a breach of international law.
Over the weekend, US Secretary of State John F. Kerry warned President Vladimir Putin of Russia that he may ‘‘find himself with asset freezes on Russian business.’’
The biggest economic risk revolves around Russia’s supply of natural gas.
Many eastern European countries rely almost entirely on those imports and even Germany, Europe’s largest economy, gets 35 percent of its supplies from Russia.
Gazprom, the Russian energy conglomerate, has threatened to end a cheap deal on gas it sells to Ukraine, and claimed it is owed about $1.55 billion.
Kathleen Brooks, market analyst at Forex.com, said the European response to the Ukraine crisis has been little more than a wag of the finger so far.
‘‘We will have to wait and see if the EU merely looks the other way when it comes to Russian-Ukrainian problems and leaves the diplomatic response to the US and UK as they try to protect their energy supplies,’’ Brooks said.