Russia has announced it is withdrawing some troops from along Ukraine's eastern border.
The German government said Russian President Vladimir Putin told Chancellor Angela Merkel about the partial withdrawal in a telephone call.
Russia's Defense Ministry said a motorized infantry battalion was being withdrawn from the southern Rostov region after ending military drills.
There was no information on the number of troops involved. A battalion can include between 300 and 1,200 troops.
U.S. State Department spokeswoman Jen Psaki said that if the reports are confirmed, "it would be a welcome preliminary step."
White House spokesman Jay Carney said the administration had not yet seen a drawdown of Russian forces.
German Foreign Minister Frank-Walter Steinmeier welcomed the Russian announcement, calling it a "small signal" that the situation might be improving.
Russia in the past month massed thousands of soldiers on its border with Ukraine, raising concerns that after annexing Crimea it might invade other parts of Ukraine.
The Kremlin said Putin also told Merkel in their telephone call that Ukraine needs constitutional reforms to protect the interests of residents of the country's different regions.
Putin has previously spoken of the need to protect the interests of ethnic Russians and Russian-speakers in Ukraine.
The Ukrainian Foreign Ministry was cautious in its statements regarding Russian troop movements.
"We have information that the Russian Federation is carrying out unfathomable maneuvers on the borders with Ukraine -- in some border places they are taking away troops, in others they are coming closer," ministry spokesman Evhen Perebiynis told reporters in Kyiv. "Such actions cannot fail to cause concern especially since we today do not have a clear explanation from the Russian Federation about the aims of these movements."
Moscow Eyes Transdniester
Merkel's spokesman said that the two leaders talked about further steps to "stabilize" the situation in both Ukraine and in Moldova's Russian-speaking separatist Transdniester region.
The Kremlin said Putin told Merkel
that measures were needed to remove what a Russian statement called a "blockade" on Transdniester.
Putin made a similar claim of a Transdniester "blockade" in a telephone call with U.S. President Barack Obama on March 28.
Moldova's government and the United States have rejected the Russian claim.
Transdniester declared independence from Moldova in 1990. The two sides fought a brief war in 1992 that ended when the Russian military intervened on the side of Transdniester.
Transdniester's independence is not recognized by any country.
Russia still has around 1,400 troops in the territory. There has been some concern about a possible Russian incursion across Ukraine to occupy Transdniester
The Russian Foreign Ministry said Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry had spoken by telephone.
The talk came one day after Kerry and Lavrov met in Paris and agreed to try to resolve the crisis through diplomacy.
Kerry has called for the withdrawal of Russian forces from the border to deescalate the situation.
Russian Prime Minister Dmitry Medvedev on March 31 visited Crimea, in the highest-level visit by an official from Moscow since Russia seized the territory.
Medvedev toured the regional capital Simferopol at the head of a delegation of cabinet ministers, and later visited Sevastopol, where Russia's Black Sea Fleet has a base.
Medvedev announced that Crimea would become a "special economic zone" to attract investors.
Ukraine denounced Medvedev's visit, describing it as a "crude violation of the rules of international behavior."
NATO foreign ministers are due in Brussels to discuss the Ukrainian crisis on April 1.
NATO Secretary-General Anders Fogh Rasmussen told RFE/RL's Radio Free Afghanistan in an interview that "we have agreed with Ukraine to strengthen our cooperation within our NATO-Ukraine partnership within the NATO-Ukraine Commission," adding, "[T]omorrow we will have a political level meeting in the NATO-Ukraine Commission and I expect assistance to be made as to how we can further develop our partnership with Ukraine."
Diplomats say NATO foreign ministers will likely debate a range of options from stepped-up military exercises and sending more forces to eastern members states, to the permanent basing of alliance forces there.
At a meeting with Ukrainian Foreign Minister Andriy Deshchytsya, the NATO ministers are also expected to offer help to make Ukraine's armed forces more efficient.
NATO member countries have denounced Russia's annexation of Crimea as a violation of international law and say they will not recognize it.
Based on reporting by Reuters, AFP, RFE/RL, and AP