WASHINGTON — Two U.S. senators said that Russia had denied them visas, amid disagreement within Washington and among U.S. allies over whether the country should be readmitted to the Group of Seven.

Sen. Chris Murphy, D-Conn., said Tuesday that he had planned to visit Russia as part of an upcoming congressional delegation including Democrats and Republicans. Sen. Ron Johnson, R-Wisc., said Monday that he was also denied a visa. Both lawmakers are members of the chamber's Foreign Relations Committee and have been critical of Russia in the past.

President Donald Trump said last week it would be appropriate to let Russia return to the G-7 group of advanced industrialized countries, telling reporters that former President Barack Obama had wanted Russia out of what was the G-8 but he thought it was "much more appropriate" to include the country.

Other G-7 countries have objected.

"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," Murphy said in a statement.

Russia repeatedly has denied visas to U.S. lawmakers in recent years, especially those who have pushed for sanctions against Moscow over its aggression toward Ukraine and interference in U.S. elections.

In a statement posted to Twitter, the Russian embassy claimed that Johnson "did not apply for a visa at our Embassy and did not inform about his plans."

Separately, a group of senior Democratic senators said Tuesday they had written to Trump expressing strong opposition to readmitting Russia to the G-7, citing its invasion of Ukraine's Crimea.

The letter was signed by Sens. Chuck Schumer, the Democratic leader in the Senate, as well as Jack Reed, Bob Menendez and Mark Warner, the top Democrats on the Armed Services, Foreign Relations and Intelligence committees, respectively.