Russia has reportedly agreed to abide by the limits of a nuclear arms pact it reached with the U.S. years ago after the agreement expired last week — as long as Washington does the same.

The New START Treaty's expiration, which occurred on Feb. 5, leaves the nations with the two largest atomic arsenals with no restrictions for the first time in more than a half-century, The Associated Press reported. The expiration has fueled fears of a possible unconstrained nuclear arms race.

In September, President Vladimir Putin said Russia would abide by the nuclear arms deal for another year after its expiration date as long as the U.S. followed suit, the AP reported. However, President Donald Trump has said he wanted China to be part of a new pact, something that Beijing has rejected, according to the AP.

"Rather than extend 'NEW START' (A badly negotiated deal by the United States that, aside from everything else, is being grossly violated), we should have our Nuclear Experts work on a new, improved, and modernized Treaty that can last long into the future," Trump wrote on Truth Social upon the treaty's expiration.

WORLD ENTERS UNCHARTED ERA AS US-RUSSIA NUCLEAR TREATY EXPIRES, OPENING DOOR TO FASTEST ARMS RACE IN DECADES

In response to Fox News Digital's request for comment on the now-expired treaty, the White House pointed to the president's Truth Social post.

Russian Foreign Minister Sergey Lavrov spoke to lawmakers about the treaty, saying Moscow would "act in a responsible and balanced way on the basis of analysis of the U.S. military policies," the AP reported.

Lavrov added that "we have reason to believe that the United States is in no hurry to abandon these limits and that they will be observed for the foreseeable future."

"We will closely monitor how things are actually unfolding," Lavrov said. "If our American colleagues’ intention to maintain some kind of cooperation on this is confirmed, we will work actively on a new agreement and consider the issues that have remained outside strategic stability agreements."

TRUMP CALLS FOR NUCLEAR EXPERTS TO WORK ON 'NEW, IMPROVED, AND MODERNIZED TREATY'

The New START Treaty was signed in 2010 by President Barack Obama and his Russian counterpart, Dmitry Medvedev, and was entered into force on Feb. 5, 2011. 

The treaty gave the U.S. and Russia until Feb. 5, 2018, to meet the central limits on strategic offensive arms. The treaty caps each side at 700 deployed ICBMs, SLBMs and nuclear-capable heavy bombers; 1,550 deployed warheads; and 800 deployed and non-deployed launchers and bombers. The parties were then obligated to maintain the limits as long as the treaty remained in force, which it did until last week.

The expiration of the treaty comes just after a meeting involving U.S. and Russian officials in Abu Dhabi. Axios previously reported that the two nations were closing in on a deal to observe the treaty for at least six months after its expiration. The outlet added that during the six-month period there would be negotiations for a new deal.

The State Department did not immediately respond to Fox News Digital's request for comment.