MOSCOW, March 20 (Reuters) - Russia will boost its military presence in Crimea to protect against external threats, state news agency Itar-Tass quoted Deputy Defence Minister Yuri Borisov as saying on Thursday as lawmakers voted to annex the Ukrainian region.
"It will be necessary to develop the military infrastructure on the peninsula so that Crimea would be a worthy representative of the Russian Federation and be protected against all possible encroachments," he said.
Russia is the world's third largest military spender behind the United States and China and plans to spend 20 trillion roubles ($556.84 billion) by 2020 to revamp its armed forces, a target Borisov said Russia would not sacrifice.
He gave no immediate details, but boosting Russia's military presence would probably entail combining its current Black Sea Fleet facilities with Ukrainian bases where Russian troops have taken control.
The Black Sea Fleet is made up of 40 combat ships, 28 of which are on active duty while others undergo modernisation, according to U.S.-based analyst Dmitry Gorenburg.
Russian Foreign Minister Sergei Lavrov said Ukrainian soldiers left outside the bases taken over by Russian troops would be able to choose whom to serve.
"All Ukrainian servicemen on the territory of Crimea have been proposed a free choice - either leave the territory of Crimea or ... stay in Crimea and serve in the Black Sea Fleet of the Russian Federation," he said, speaking at parliament.
Russia's seizure of Crimea has brought ties between Moscow and the West to their lowest point since the end of the Cold War.
($1 = 35.9170 Russian Roubles) (Reporting by Thomas Grove; Editing by Steve Gutterman and Andrew Roche)