Updated

The top Republican on the Senate Foreign Relations Committee accused the Obama administration on Sunday of showing “wishy-washiness” toward Russian President Vladimir Putin as he attempts to take control of a Ukraine peninsula.

Tennessee Sen. Bob Corker said Secretary of State John Kerry is sending the wrong message by saying U.S. opposition to Putin’s military troops taking control of facilities in the Crimea peninsula was “not a threat” and “nothing personal.”

“Our administration has created an air of permissiveness,” Corker told “Fox News Sunday.” “We have to show more resolve. It’s not helpful. It shows wishy-washiness.”

Putin has sent troops into the region amid Ukraine’s political upheaval and has defended his efforts by saying he is trying to protect Russian interests in Crimea amid widespread protests, which last month led to the ouster of pro-Russian Ukraine President Viktor Yanukovych.

On Sunday, the Crimea residents will vote on whether to be annexed by Russia -- as part of what is considered a Kremlin-backed referendum.

New Jersey Democratic Sen. Bob Menendez, the chairman of the Foreign Relations committee, told Fox that the United States has to be more firm with Putin because he has “started a game or Russian Roulette … and he will see how far he can go.”

Menendez's remarks come as residents of the Crimea region began voting on ratifying the regional parliament's decision to break away from Ukraine and seek annexation by Russia.

The referendum has been condemned as illegal by the United States and European countries.

The vote took place several weeks after Russian-led forces took control of Crimea, a predominantly ethnic Russian region. Its residents say they fear the Ukrainian government that took over when Yanukovych was ousted last month will oppress them.

The European Union is taking steps to increase sanctions against Russia over what many believe is a planned annexation of Crimea, as Moscow has changed from a wary partner to a diplomatic adversary in the space of a few months.

EU foreign ministers will decide on Monday whether to impose asset freeze and visa sanctions and, if so, who to target.

EU diplomats were working feverishly over the weekend to set up a list of Russian and Moscow-leaning officials from Ukraine who have been involved in pushing for the southern peninsula's secession and possible annexation.  Diplomats said member states arrived at weekend talks with different suggestions, so a common list could be drawn up for Monday's meeting of the 28 foreign ministers to make a final decision.

The Associated Press contributed to this report.