WASHINGTON — The United States prepared Monday to impose sanctions on high-level Russian officials involved in the military occupation of Crimea, as the escalating crisis in Ukraine prompted turmoil in global markets, pounding the Russian ruble and driving up energy prices.

The Obama administration suspended military ties to Russia, including exercises, port visits and planning meetings, just a day after calling off trade talks. If Moscow does not reverse course, officials said they would ban visas and freeze assets of select Russian officials in the chain of command as well as target state-run financial institutions. Congressional leaders signaled that they would follow with sanctions of their own, and quickly approve economic aid for the fragile, new pro-Western government in Ukraine.

The besieged Kiev government said Monday that the Russians had deployed 16,000 troops in the region over the past week and had demanded that Ukrainian forces there surrender within hours or face armed assault. While Russia denied it had issued any ultimatums, it was clearly moving to strengthen its control over Crimea, the largely Russian-speaking peninsula in southern Ukraine where Moscow has long maintained a military base.