Sergei Grits, Associated Press
Pro Russian masked armed militants guard barricades near Slovyansk, eastern Ukraine, Wednesday, April 30, 2014.

BRUSSELS — Several European foreign ministers on Monday threatened to impose further sanctions against Russia if it fails to cooperate with Ukraine's proposed peace plan and doesn't stop the flow of arms and militants across its border into eastern Ukraine.

Russia is "conducting a propaganda war with full speed ahead and no signs of them closing the border," said Swedish Foreign Minister Carl Bildt.

Armed militants and even tanks continue to cross the border into eastern Ukraine, he asserted. "If the Russians say they don't know how to close borders, I don't think that's a particularly credible statement," Bildt added.

British Foreign Secretary William Hague said the European Union will be able to agree on further sanctions against Russia at a summit of the bloc's 28 leaders Friday, if necessary. "Those measures are ready to take," he said.

"We look to Russia to take actual action to stop the flow of arms over the border into eastern Ukraine, to encourage illegal armed groups to stop what they are doing there now," Hague said.

The EU meeting in Luxembourg Monday was also being attended by Ukraine's new foreign minister, Pavlo Klimkin, who was set to brief his colleagues on the peace plan proposed by President Petro Poroshenko. It includes a cease-fire in its battle against pro-Russian separatists in eastern Ukraine. The plan also calls for an inclusive political dialogue, suggests a decentralization of power to give regions more political authority and foresees measures to protect the language rights of Russian speakers in eastern Ukraine.

"We now look to Russia to support the peace plan," Hague insisted.

Lithuanian Foreign Minister Linas Linkevicius also called on Russia to stop the flow of militants and heavy weapons to avoid tougher sanctions.

The EU and the United States have so far mainly ordered visa bans and asset freezes for a number of officials but have refrained from imposing broader economic sanctions. EU leaders will review the situation Friday.

Reacting to Poroshenko's plan, Russian President Vladimir Putin on Sunday expressed support for the cease-fire and called on both sides to negotiate.

Russian Foreign Minister Sergei Lavrov said Monday during a visit to Armenia that Moscow supports the initiative to launch a political dialogue in Ukraine as the only way to "guarantee the equal rights and freedom of citizens in all regions of the country."

Avet Demourian in Yerevan, Armenia contributed reporting. Follow Juergen Baetz on Twitter at