The United States said Monday it would welcome any Russian move to pull its forces back from the Ukrainian frontier, but did not confirm reports that it has begun to do so.

"If reports that Russia is removing some troops from the border region are accurate, it would be a welcome preliminary step," US State Department spokeswoman Jen Psaki said.

"We would urge Russia to accelerate this process," she added, in a statement issued during US Secretary of State John Kerry's visit to Israel.

"We also continue to urge Russia to engage in a dialogue with the government in Kiev to de-escalate the situation, while respecting the sovereignty and territorial integrity of Ukraine."

US officials said that Kerry had spoken to his Russian counterpart Sergei Lavrov by telephone from his plane before arriving in Israel.

Earlier, Ukraine had reported that Russian troops had partially pulled back from its border, reducing fears that Moscow may launch an operation to grab more territory from its neighbor.