Armed men, believed to be Russian servicemen, take cover behind an armored vehicle as they attempt to take over a military base in the Crimean town of Belbek, near Sevastopol.

March 22, 2014 Armed men, believed to be Russian servicemen, take cover behind an armored vehicle as they attempt to take over a military base in the Crimean town of Belbek, near Sevastopol. Shamil Zhumatov/Reuters

After an ultimatum to abandon the base and an hours-long standoff, Russian troops in at least four armored vehicles seized control of one of the last Ukrainian military outposts in Crimea.

Ukraine’s government mobilized reservists and approved an emergency military buildup a day after the disputed province of Crimea voted to secede from the country and become part of Russia.

But with its armed forces woefully ill-trained and poorly equipped after years of underfunding, a frustrated Ukraine continued to focus on diplomacy first.

Political leaders here hurled harsh words at Moscow and refused to give up Crimea as lost. But even as the government in Kiev took steps to shore up national defenses, it renewed calls for a diplomatic solution. Amid concerns about possible further Russian intervention in Ukraine’s restive east and south, Kiev hoped for the best — ­progress in efforts to resolve the crisis — while also preparing for the worst.

Parliament approved a presidential decree mobilizing some of the country’s 40,000 reservists and agreed to divert $600 million from other parts of Ukraine’s budget to buy weapons, repair equipment and boost training over the next three months — a major commitment for a cash-strapped country.

At least some reservists will be deployed in the coming days and weeks in the newly formed national guard to protect sites categorized as “strategic” and could be used as peacekeepers at volatile protests in eastern cities such as Kharkiv and Donetsk, where clashes between pro-

Russian and pro-Kiev activists have left three dead and dozens wounded in recent days.

The United States and European nations announced sanctions against Russian officials over Crimea's vote to break away from Ukraine. The Post's Douglas Jehl, Scott Wilson, and Anne Gearan explain the implications. (Jonathan Elker, Jeff Simon and Kate M. Tobey/The Washington Post)

Yet the challenge ahead for Ukraine was clear Monday at a military base in Novi Petrivtsi, near Kiev, where hundreds of the first recruits for the new national guard marched back and forth between training exercises. The earnest men — some teenagers, others approaching 50 — are meant to beef up the defenses of a nation where only a fraction of the 130,000-strong military is considered combat-ready.

In a worst-case scenario — a major military incursion by Russia into mainland Ukraine — some of those men could find themselves on the front lines. Some — engineers and students, college professors and factory workers — seemed wildly out of place in uniform. They trained in the freezing rain Monday with equipment that was old when the Berlin Wall fell.

“The only time I’ve shot a gun was on a hunting trip,” said Grigoriev Ruslan, a 19-year-old training for deployment. He said he had tried to join the military earlier but had been rejected because of severe injures he had suffered in an auto accident.

“I arrived two days ago and haven’t had time to think about being scared yet,” Ruslan said. “We don’t want war, but we are prepared to do what we need to for our country. I will fight for Ukraine.”

At the same time, a sense of bitterness gripped some political leaders, who said they think the West has done too little to force Russia to retreat. They referred to the 1994 Budapest Memorandum, in which the United States, Britain and Russia reaffirmed their commitment to Ukraine’s territorial sovereignty after the breakup of the Soviet Union and in which Kiev agreed to surrender its nuclear stockpile.

A wave of regret that Ukraine had given up its most powerful potential deterrent — nuclear weapons — has reverberated through Kiev in recent days. “I can tell you that had we kept them, Russia would never have entered Crimea,” said Anatoliy Hrytsenko, the Ukrainian defense minister from 2005 to 2007.

Like many here, he argued that Russia has violated the 1994 deal and that the West has an obligation to act more boldly than it has to protect Ukraine. He called for U.S. and European warships and aircraft to be re­located to the region in an unequivocal show of force. He chided leaders in Western Europe and Washington for interpreting the deal as a general commitment for unspecified support rather than as a document with the weight of a mutual defense treaty.

What the West “fails to realize is that this is not just Crimea,” Hrytsenko said. “Do you think Russia will stop there? And how do you think such weakness will be seen in Iran and Syria? This is a question of global credibility.”

Others were more cautious in their remarks. Officials here have made requests for Washington to sell Ukraine the weapons and military equipment it needs to update an arsenal in woeful condition. But asked Monday whether such sales should go forward after Sunday’s referendum in Crimea, Vitali Klitschko, a politician and former boxing champion who is running for president, refrained from answering directly. “That is a very sensitive question,” he said.

The suggestion is that even as Ukraine seeks more leverage against Russia, it is trying to avoid provoking Moscow into taking further action. Klitschko added that there is no serious thought being given to cutting water, electricity or natural gas supplies to Crimea — a region Kiev still considers part of Ukraine despite Sunday’s vote.

But to the extent it can, Ukraine is remaining defiant.

With some of his troops on bases in Crimea surrounded by Russian forces, Defense Minister Ihor Tenyukh said Ukraine would not back down even as the potential separation of Crimea from the rest of Ukraine moves forward. He said there were no plans to abandon bases and installations in Crimea.

“Crimea is, was and will be our territory,” Tenyukh said.

A truce between the two sides is in place until March 21.