Updated

The White House brushed off concerns Friday that, with the crisis in Crimea intensifying, now might not be the best time for President Obama -- and his vice president -- to go on vacation.

The travel schedules of both the president and Vice President Biden have come under scrutiny, given the rapidly changing situation in Ukraine. Obama, already in Florida to talk about education, was planning to spend some family time this weekend in Key Largo, Fla., where he arrived late in the day. Biden, meanwhile, will be in the Virgin Islands.

Despite some apparent discussion over cutting the president's trip short, White House spokesman Josh Earnest indicated the president would be able to handle the crisis from out of the office.

"The president over the course of a very busy week has maintained his schedule and his ability to monitor ongoing events in Ukraine. I would anticipate that he'll do the same thing this weekend," Earnest said. "And the fact of the matter is what the president is doing this weekend in Florida is essentially what the president will be doing if he stayed back at the White House. It's just that the weather will be a little warmer."

He said Obama plans to spend time with his wife and daughters while in the Keys. "There are some recreational amenities on the property, including workout facilities, tennis courts, a couple of golf courses," he noted.

But he also said Obama is keeping in touch with allies in Europe and other world leaders. "So if there is an opportunity for the president to enjoy some of those amenities, then he'll do that. But we'll have to see," he said. He noted that Deputy National Security Adviser Tony Blinken is traveling with the president. And Obama has "the regular assortment of communications tools that will allow him to convene in a secure fashion meetings with his national security team, if necessary."

Obama spoke Thursday with Russia's Vladimir Putin for the second time since the crisis erupted, but Russia showed little sign of backing down.

Foreign Minister Sergey Lavrov warned U.S. Secretary of State John Kerry that sanctions over Russian actions in Crimea could backfire, the ministry said in a statement. In a telephone conversation, Lavrov urged the U.S. not to take "hasty, poorly thought-out steps that could harm Russian-U.S. relations, especially concerning sanctions, which would unavoidably boomerang on the U.S. itself," the statement said.

Meanwhile, a military truck broke down the gates of a Ukrainian base in the Crimean port city of Sevastopol and the installation was under siege by pro-Russian troops on Friday, the Interfax news agency reported. No shots have been fired.

About 100 Ukrainian troops are stationed at the base, Interfax reported, citing a duty officer and Ukraine's defense ministry.

In the week since Russia seized control of Crimea, Russian troops have been neutralizing and disarming Ukrainian military bases on the Black Sea peninsula. Some Ukrainian units, however, have refused to surrender.

Crimea's new leader has said pro-Russian forces numbering more than 11,000 now control all access to the region and have blockaded all military bases that haven't yet surrendered.

The Pentagon estimates there are actually about 20,000 Russian troops in Ukraine, as additional forces have gone into the country over the last week.

Rear Adm. John Kirby said Defense Secretary Chuck Hagel spoke with Ukraine Defense Minister Ihor Tenyuh on Friday. He said Tenyuh asked Hagel to consider having the U.S. military provide Ukraine with technical advice, including on humanitarian and disaster relief operations. Hagel said he would consider the request. The U.S. has already sent fighter jets to the region to boost its NATO presence.

The Associated Press contributed to this report.