Ukraine Mobilizes For War with Russia

By Natalia Zinets and Alissa de Carbonnel

KIEV/BALACLAVA, Ukraine, March 2 (Reuters) - Ukraine mobilized for war on Sunday and Washington threatened to isolate Russia economically, after President Vladimir Putin declared he had the right to invade his neighbor, creating Moscow's biggest confrontation with the West since the Cold War.

"This is not a threat: this is actually the declaration of war to my country," Ukraine's Prime Minister Arseny Yatseniuk, head of a pro-Western government that took power when Russian ally Viktor Yanukovich fled last week, said in English.

Putin obtained permission from his parliament on Saturday to use military force to protect Russian citizens in Ukraine, spurning Western pleas not to intervene.

Russian forces have already bloodlessly seized Crimea - an isolated Black Sea peninsula where Moscow has a naval base. On Sunday they surrounded several small Ukrainian military outposts there and demanded the Ukrainian troops disarm. Some refused, leading to standoffs, although no shots were fired.

Russia has staged war games with 150,000 troops along the land border, but so far they have not crossed. However, pro-Russian demonstrators have marched in the east of the country and have raised Russian flags over government buildings in several cities, in what Kiev says is a move orchestrated by Moscow to justify a wider invasion.

Ukraine's security council ordered the general staff to immediately put all armed forces on highest alert.

The Defense Ministry was ordered to stage a call-up of reserves - theoretically all men up to 40 in a country with universal male conscription, though Ukraine would struggle to find extra guns or uniforms for significant numbers of them.

U.S. Secretary of State John Kerry condemned Russia for what he called an "incredible act of aggression" and threatened "very serious repercussions".

"You don't just, in the 21st century, behave in 19th century fashion by invading another country on completely trumped-up pretext," Kerry told CBS program Face the Nation.

Kerry said Moscow still had a "right set of choices" to defuse the crisis. Otherwise, G8 countries and other nations were prepared to "to go to the hilt to isolate Russia".

"They are prepared to isolate Russia economically. The rouble is already going down. Russia has major economic challenges," he said. He mentioned visa bans, asset freezes and trade isolation as possible steps. A Kremlin spokesman declined to comment after Kerry's remarks.