Russian officials claim that their U.S. counterparts are unwilling to sit down for discussions related to alleged violations of a nuclear arms treaty between the U.S. and Russia.

A spokesman for Russian Defense Minister Sergei Shoigu told The Associated Press on Saturday that Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE has yet to respond to a proposal from Shoigu to begin conversations between the two countries about alleged violations of the Intermediate-Range Nuclear Forces (INF) Treaty.

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The alleged lack of a response is proof, the spokesman claims, that the U.S. is uninterested in maintaining official contacts with Russia on security officials. The U.S. issued an ultimatum on Dec. 4, declaring that Washington would exit the treaty if Russia does not come into compliance with the agreement in 60 days.

The U.S. has claimed that Russia is in violation of the treaty due to a new missile, designated by NATO as the SSC-8, which the U.S. says operates in ranges banned under the treaty. Russia has denied the U.S.'s claim.

Russia, meanwhile, has accused Washington of noncompliance with the treaty. Russia, the AP reported, has taken issue with U.S. deployment of anti-missile systems — specifically, a U.S. Mk-41 vertical launching system — in Romania and Poland. According to the AP, the system can launch a number of U.S. missiles, including the sea-launched Tomahawk cruise missile, which would be banned under the treaty if it were deployed on a land-based launching system.

U.S. claims of alleged Russian violations of the INF date back to the Obama administration.

"It is time now for Russia to come to the table and stop the violations," U.S. Ambassador to NATO Kay Bailey Hutchison told reporters in October.