WASHINGTON — The United States urged Russia on Wednesday to stop its “provocation” in eastern Ukraine, warning it was preparing new sanctions against Moscow ahead of a critical international meeting in Geneva on the crisis.

As Secretary of State John Kerry was flying to the Swiss city for talks involving Russia, Ukraine and the European Union, the White House signaled new sanctions against Moscow could be imminent.

“We are actively preparing new sanctions,” White House spokesman Jay Carney said, stiffening US language from Tuesday when the State Department said Washington was considering “additional” measures.

Carney told reporters aboard Air Force One that Washington was looking to Russia at the meeting for a sign it was ready to de-escalate the tense situation in eastern Ukraine where pro-Moscow separatists have clashed with Kiev’s forces.

The State Department, too, demanded de-escalation and demobilization on the part of Russia and pro-Russian forces.

“We definitely want to see an immediate halt to that provocation,” State Department deputy spokeswoman Marie Harf told reporters.

Kerry will join the four-way talks Thursday in a bid to defuse the worsening crisis, but Washington said action by Russia was paramount.

“Talk doesn’t replace actions when it comes to what’s happening on the ground, and we will continue to prepare additional sanctions and other steps if we can’t get some de-escalation here,” Harf said.

“Clearly, the presence of armed groups that the Russians are supporting in eastern Ukraine is an incredibly pressing priority.”

While Harf described the four-way talks as “an important diplomatic step,” she appeared to downplay their potential for dramatic breakthrough.

“I wouldn’t put it all on this meeting,” she said. “Russia needs to take steps to de-escalate.”

And Carney said Russia also needed to acknowledge at the talks that the Ukrainian government had committed itself to constitutional reform.

Kerry was also set to meet separately in Geneva with Russian Foreign Minister Sergei Lavrov, his Ukrainian counterpart Andriy Deshchytsya and EU foreign affairs head Catherine Ashton.

The meetings follow tense face-offs between Ukrainian and pro-Russian forces in eastern Ukraine, and after Russian President Vladimir Putin warned Ukraine was on the brink of civil war, stoking fears of outright Russian intervention.

Harf declined to describe the situation as a civil war, saying she had not heard State Department officials use the term.

US-Russia ties “complicated”

With tensions soaring, Harf noted that Washington’s relationship with Moscow was “complicated” but remained intact.

“There are places we work together,” she said, pointing to the international talks with Iran on its nuclear weapons program, and to efforts to reduce Syria’s chemical weapons stockpiles.

“But I don’t think anyone would be surprised that the events of the last weeks and months have really been hard for the (US-Russia) relationship,” she said.

The US has backed Kiev’s right to quell separatist uprisings that started in the Crimean peninsula and have since spread to other parts of Ukraine, setting the stage for the most serious rupture in West-Russia relations since the end of the Cold War.

Washington’s priorities include getting Russia to demobilize pro-Kremlin militias which have seized control of government buildings in Ukraine’s southeast.

Putin has denied Moscow has any links to the groups.

Meanwhile US lawmakers will travel Monday to Ukraine in a show of support and to assess Obama administration engagement there, said the delegation’s leader, House Foreign Affairs Committee chairman Ed Royce.

“Ukraine is in crisis and the US should do what we can to bolster its government against Russian aggression,” Royce said.