Washington (CNN) Two US senators have been denied visas to Russia in what appears to be a retaliatory move on the part of the Kremlin amid continued tensions between the two countries.

Sen. Ron Johnson, a Wisconsin Republican, and Sen. Chris Murphy, a Connecticut Democrat, were scheduled to travel as part of a congressional delegation to Russia next week. Both said their visas for the trip were rejected.

A third member of the delegation, Republican Sen. Mike Lee of Utah, did not have his visa rejected, a spokesperson told CNN. Lee still plans to go to Russia, that spokesperson said. A Senate staffer familiar with the trip said Murphy is now going to Germany and will then be joined by Johnson for stops in Kosovo, Serbia and Ukraine. Those latter three stops were part of the original itinerary, the staffer said.

In a statement Tuesday, Murphy said, "Unfortunately, the Russian government is further isolating their country by blocking our visit and several others in recent months."

"With the collapse of recent arms control agreements and significant domestic opposition to Vladimir Putin's authoritarian rule, this is potentially a perilous moment for our two nations' fragile relationship, and it's a shame that Russia isn't interested in dialogue," he said.