The East-West split re-opened by the crisis in Ukraine hardened Wednesday when President Barack Obama threw Washington's weight firmly behind Ukraine in its stand-off with Moscow.

Obama welcomed Kiev's interim premier Arseniy Yatsenyuk to the White House and stood by his side as both leaders sternly warned Russia that Ukraine would not surrender its sovereignty.

Belarussian President Alexander Lukashenko said Wednesday he would ask Russia to station up to 15 jets in his country in response to NATO's moves over the Ukraine crisis.

"If NATO decided, together with the Americans, to ramp up their air force presence near our borders, what, should we just watch them?" the maverick leader said, speaking at a meeting of his security council.

President Vladimir Putin has seen his approval rating climb in Russia due to his strong stance on military intervention in Ukraine, several opinion polls show.

More than two out of three Russians (69 percent of those interviewed), say they back Putin's actions, a poll by the independent Levada agency found in late February after interviewing 1,603 people in 45 regions.

Standing in the shadow of a massive, grey former KGB building in a busy Vilnius street, Lithuanian pensioner Rimantas Gucas worries history could repeat itself if the West fails to stop Russia from absorbing Ukraine's Crimean peninsula.

As Lithuania marks 24 years since it broke free from the crumbling Soviet Union and a decade since it joined NATO, people here and in fellow Baltic states Estonia and Latvia are jittery over Russian moves in Crimea.

Sarah Palin offered unsolicited advice Saturday to President Barack Obama on containing Russian aggression, saying "the only thing that stops a bad guy with a nuke is a good guy with a nuke."

The Republican former vice presidential candidate used a predominantly crass tone throughout her appearance at the Conservative Political Action Conference.

A Pentagon research team is studying the body language of Russian President Vladimir Putin and other foreign leaders to better predict their behavior, officials said Friday.

The project, previously conducted under the State Department, is now backed by the Defense Department's Office of Net Assessment. Putin's psychological profile was last updated in 2012, a Pentagon official said.

Russia does not want a new Cold War, President Vladimir Putin's spokesman said on Friday, as tensions rose over Russian-backed demands by Crimea to secede from Ukraine.

Dmitry Peskov was asked on a chat show on state television whether he could foresee a return to the clash of ideologies that polarized the world between 1945 and the fall of the Berlin Wall in 1989.

Five topless activists from the Femen feminist group protested in New York's Times Square on Thursday to denounce Russia's incursion into Ukraine, asking for tougher U.S. and EU action against Moscow.

The women, whose bare chests were painted blue and yellow -- the color of Ukraine's flag -- hoisted a placard slamming Russian President Vladimir Putin's "occupation" of Crimea and another urging, "U.S.-EU, stop talking start acting".

Russian President Vladimir Putin is seeking to profit to the maximum from Ukraine's turmoil by implementing the de-facto annexation of Crimea at high speed to wrong foot an indecisive West, analysts said.

The ousting of the generally pro-Russian Ukrainian president Viktor Yanukovych was a major defeat for Putin and means that the ex-Soviet state is now swiftly aligning itself with the European Union in a historic switch away from the Kremlin.

Syria's President Bashar Assad has expressed his "solidarity" with Russian President Vladimir Putin's position on the crisis in Ukraine, state media reported on Thursday.

In a telegram, Assad "expressed... Syria's solidarity with Putin's efforts to restore security and stability to Ukraine in the face of attempted coups against legitimacy and democracy in favor of radical terrorists", state news agency SANA said.