President Barack Obama and Russian President Vladimir Putin agreed to keep talking — but little else — in a telephone call Monday over Moscow's support for separatist protesters in Ukraine, the U.S. and Russia said.
A senior administration official told NBC News that Putin sought the discussion, which was described as "frank and direct."
The official said Obama made it clear that "Russia's actions are neither consistent with or conducive" to a settlement to the upheaval in Ukraine's Russian-speaking eastern and southern regions, where pro-Moscow gunmen demanding closer ties with Russia have seized or blocked government buildings in at least nine cities.
In a statement, the White House added that Obama "expressed grave concern about Russian government support for the actions of armed, pro-Russian separatists who threaten to undermine and destabilize the government of Ukraine."
He told Putin that "all irregular forces in the country need to lay down their arms" and "depart the buildings they have seized" and said Russia must withdraw its troops from Ukraine's border, the White House said.
The Kremlin objected that Washington's reading of its intentions in Ukraine were "based on inaccurate information," saying in a statement Monday that the "current Ukrainian authorities" were to blame for the showdown through their "unwillingness and inability to take into account the interests of the Russian and Russian-speaking population."
The phone call came two days after a Russian attack warplane made more than a dozen passes over a U.S. Navy guided-missile destroyer Saturday in the western Black Sea — an action that White House press secretary Jay Carney described Monday as a "provocative and unprofessional" display that only heightened concerns about Russia's "attempts to destabilize Ukraine."
"I can assure you that Russia's further transgressions and provocations will come with a cost," Carney said at the daily White House news briefing.
Carney wouldn't tally what those costs might be, saying only that "we are working with our partners and assessing for ourselves what response we may choose."
The White House confirmed that Obama also spoke Monday with French President Francoise Hollande to discuss the "significant additional costs" for what it called Moscow's "support and coordination" of the protests in Ukraine.
"I can assure you that Russia's further transgressions and provocations will come with a cost."
France is a leading member of the European Union, which approved new measures to bolster Ukraine against the protests at a meeting of its Foreign Affairs Council in Luxembourg on Monday.
The council eliminated customs duties on 95 percent of European imports from Ukraine — which it said will save Ukrainian exporters almost $700 million a year.
British Foreign Secretary William Hague said the assistance would give a big shot in the arm to the Ukrainian economy ahead of Thursday's talks in Geneva among the E.U., Russia, the U.S. and Ukraine.
The meeting "is an important opportunity for Russia to show that it is prepared to use diplomacy to de-escalate the situation," Hague said.
"But it has to be said that there has been no sign of that in Russia's actions so far," he said.
Andrea Mitchell and Catherine Chomiak of NBC News contributed to this report.