The Obama administration's sanctions against Russia “haven't worked,” Sen. Ron Johnson, R-Wis., said on Sunday, insisting that Russian President Vladimir Putin would respond only to “action, strength and resolve” in the showdown over the Ukrainian crisis.

President Obama has imposed sanctions on individuals and businesses with close ties to Putin but has resisted wide-ranging penalties against sectors of the Russian economy in the wake of the annexation of Crimea.

In a joint press conference with German Chancellor Angela Merkel Friday, Obama threatened sectoral sanctions against the Russian economy if the Kremlin interfered in elections planned for May 25 in Ukraine.

But Johnson said those threats did little to deter Putin.

“The sad fact is sanctions haven't worked,” Johnson said on CNN's “State of the Union."

“All the sanctions, the threats of sanctions really have had very little effect, and that's unfortunate,” he added. “Vladimir Putin is only going to respond to action, strength and resolve. He's not going to respond to words, and that's certainly what we hear when we go over to Ukraine.”

Democrats counter that the White House can't move ahead with tougher sanctions on Russia without the support of European allies, nations whose economies would be directly impacted by such punishments.

“What President Obama is trying to do is work in conjunction with our European allies,” said Rep. Eliot Engel, D-N.Y., also appearing on the CNN program. “They are much more reluctant to do anything against Russia because they rely on Russia for their energy needs.”