Two top House Republicans urged the Obama Administration to hold Russia accountable for perceived violations of a Cold War-signed nuclear arms pact in a letter penned Wednesday. It was another example of rising diplomatic and military tensions between the two superpowers, according to Defense News.

Armed Services committee chairman Mac Thornberry, Texas, and Intelligence committee chair Devin Nunes, California, each expressed “concern” and called it President Barack Obama’s “failure” to force Russia to comply with the landmark 1987 Intermediate-Range Nuclear Forces Treaty (INF).

“The I.N.F. Treaty is the only arms control treaty that succeeded in eliminating a class of nuclear arms,” the letter reads. “It has become apparent to us that the situation regarding Russia’s violation has worsened and Russia is now in material breach of the treaty.”

The letter came on the same day the New York Times reported Russia was going forward with plans for a ground-launched cruise missile program. That is in violation of the INF and comes two years after the Obama administration first attempted to call President Vladimir Putin’s government accountable for its actions.

American officials are reportedly concerned that Russia’s claim it is making the missiles for a flight-test program is wrong, and rather a means to produce the treaty-violating weapons of war.

The INF, signed by former U.S. President Ronald Reagan and Soviet leader Mikhail Gorbachev as the decades-long Cold War was de-escalating, specifically hinders both the U.S. and Russia from creating and owning ground-launched ballistic or cruise missiles with a range of 300 to 3,400 miles, the Times reported.

The U.S. and Russia have seen their tenuous relationship deteriorate a great deal in the last two years. Russia’s annexation of the Crimea from Ukraine as well as sending troops to the Eastern European nation two years ago worsened the countries’ ties. Russia has continued bombing of the Syrian capital city Aleppo, and alleged meddling by hacking to influence the U.S. presidential elections have all soured the superpowers’ relationship.

Russia has also said it is considering expanding its global military presence with possible bases in Cuba, Vietnam, and elsewhere after opening a permanent base in Syria recently. Its Defense Ministry said Thursday it had conducted drills with the Iskander-M missiles in Luba, located roughly 60 miles from Estonia’s eastern border, the Associated Press reported.