John Kerry warns Russia against "wrong choices" in Ukraine

WASHINGTON -- More than 8,000 Russian troops were taking part in training exercises near the border with Ukraine Thursday, a show of military might as U.S. Secretary of State John Kerry heads to London to meet with his Russian counterpart to discuss the crisis in Crimea.

CBS News' Margaret Brennan reported that Kerry's trip represented an 11th-hour attempt by the Obama administration to broker a diplomatic solution to the standoff between old Cold War foes ahead of a critical vote this weekend that could precipitate Russia taking control of the Crimean Peninsula -- currently a semi-autonomous republic of Ukraine.

Kerry was to tell Russian Foreign Minister Sergey Lavrov, once again, that his military must pull back from Crimea or face harsh sanctions.

"We are ready for any eventuality," Likhachev said in Moscow, according to the Reuters news agency. "We will mirror (any actions)."

Kerry has delivered the threat of sanctions from Washington before, but the clock is ticking down; on Sunday, a referendum in Crimea will lead the region's parliament to decide whether to secede from Ukraine and possibly return to Russian control.

The U.S. and European nations have said they will not recognize the referendum as legitimate, arguing the Ukraine's new government in Kiev must be part of any process to decide the future of current Ukrainian territory. The population of Crimea, however, is largely ethnic Russian, and many there are hugely supportive of the upcoming chance to formally place their region back under the administration in Moscow.

"My hope is that as a consequence of diplomatic efforts over the next several days, that there will be a re-thinking of the process that's been put forward," said Mr. Obama.

Yatsenyuk said he would welcome direct talks with Moscow.

"My message to President Putin: Mr. Putin, tear down this wall, the wall of war, intimidation, and military aggression," said Yatsenyuk, urging the Russian leader to drop his flat refusal to recognize the new Ukrainian government or hold any discussion with its representatives.

Putin, for his part, reiterated his stance Thursday that, "Russia was not the initiator of the circumstances that have taken shape" in the Ukraine.

Regardless of who initiated it, in four days, Crimea is expected to vote to break off from Ukraine. Soon after that, the Russian parliament will decide whether to accept it as part of the Russian Federation.

If that were to happen, Kerry told lawmakers on Wednesday, it would trigger extremely punishing sanctions against Russia.

"It can get ugly fast if the wrong choices are made," said Kerry, "it can get ugly in multiple directions."

The question now, reported Brennan, is whether the U.S. can persuade Russia to back off. If not, President Obama said there will be costs for Russia, and not just in the form of sanctions from Washington.

On Monday, the European Union is expected to slap its first sanctions on Russia since the Cold War.

German Chancellor Angela Merkel said Thursday that Russia risks "massive" political and economic consequences if Moscow does not enter into "negotiations that achieve results" over the situation in Ukraine.

In an address to Parliament, Merkel told lawmakers the only way out of the crisis is through diplomacy and assured them that "the use of the military is no option."

But, she said, the European Union and other western nations would soon freeze bank accounts and implement travel restrictions if Russia refused to enter "negotiations that achieve results and aren't just a play for time."