MOSCOW/WASHINGTON – Russia and the United States recognize the need to begin negotiations on the New Strategic Arms Reduction Treaty (New START) as soon as possible, the Kremlin said on Friday.

The issue was discussed during recent talks in Abu Dhabi, the capital of the United Arab Emirates, Kremlin spokesman Dmitry Peskov said, adding that both sides reached an understanding on the need to adopt responsible positions.

He said the work in Abu Dhabi was constructive but at the same time "very difficult," adding that discussions would continue.

Delegations from Russia, the US, and Ukraine took part in the second round of trilateral talks on Ukraine in Abu Dhabi on Wednesday and Thursday. Russia and Ukraine agreed to a large-scale prisoner exchange but failed to achieve substantive breakthroughs on core issues such as territorial arrangements and a ceasefire.

US to maintain nuclear deterrent

US Secretary of State Marco Rubio on Friday vowed that the US will maintain a credible and modernized nuclear deterrent after the expiration of New START.

He accused Russia of noncompliance with the New START, the last US-Russia nuclear arms control treaty, which expired on Thursday.

Rubio vowed that his country will negotiate from a position of strength and maintain a credible, modernized US nuclear deterrent while seeking to reduce global nuclear threats.

"We understand that this process can take time. Past agreements, including New START, took years to negotiate and were built upon decades of precedent," he added, suggesting a strategic vacuum may last for a long time.

As the world's two largest nuclear powers, the US and Russia together possess about 87 percent of the global nuclear arsenal.

Following the lapse of New START, for the first time in more than half a century, the world has entered a period in which US-Russian strategic nuclear forces are subject to no binding limits, no inspections and no transparency.