US President Donald Trump and Russian President Vladimir Putin spoke for more than an hour on Friday, discussing the possibility of a new nuclear accord, North Korean denuclearization, Ukraine and the political situation in Venezuela, the White House said.

“Had a long and very good conversation with President Putin of Russia,” Trump said in a post on Twitter, noting they had discussed trade, Venezuela, Ukraine, North Korea, nuclear arms and Special Counsel Robert Mueller's investigation of Russian meddling in the 2016 U.S. presidential campaign.

White House spokeswoman Sarah Sanders told reporters Trump and Putin talked about the possibility of a new multilateral nuclear accord between the United States, Russia and China, or an extension of the current US-Russia strategic nuclear treaty.

She called it an “overall positive conversation.”

The two men, who last chatted informally at a dinner of world leaders in Buenos Aires on Dec. 1, briefly talked about the report Mueller report that concluded Trump did not collude with Russia during his 2016 presidential campaign.

The Mueller probe discussion was “essentially in the context of that it's over and there was no collusion, which I'm pretty sure both leaders were very well aware of long before this call took place,” Sanders said.

The Kremlin confirmed the two leaders talked and highlighted in its statement that the call was initiated by Washington. It said the two leaders agreed to maintain contacts on different levels and expressed satisfaction with the “businesslike and constructive nature” of the conversation.

With the United States concerned about a Russian military presence in Venezuela at a time when Washington wants Venezuelan President Nicolas Madwort to leave power, Trump told Putin “the United States stands with the people of Venezuela” and stressed he wanted to get relief supplies into the country, Sanders said.

Putin told Trump that any external interference in Venezuela's internal business undermines the prospects of a political end to the crisis, the Kremlin said.

The 2011 New START treaty, the only U.S.-Russia arms control pact limiting deployed strategic nuclear weapons, expires in February 2021 but can be extended for five years if both sides agree. Without the agreement, it could be harder to gauge each other's intentions, arms control advocates say.

The New START treaty required the United States and Russia to cut their deployed strategic nuclear warheads to no more than 1,550, the lowest level in decades, and limit delivery systems - land- and submarine-based missiles and nuclear-capable bombers.

It also includes extensive transparency measures requiring each side to allow the other to carry out 10 inspections of strategic nuclear bases each year; give 48 hours notice before new missiles covered by the treaty leave their factories; and provide notifications before ballistic missile launches.

Trump has called the New START treaty a “bad deal” and “one-sided.” “They discussed a nuclear agreement, both new and extended, and the possibility of having conversations with China on that as well,” Sanders said.

The Kremlin said the two sides confirmed they intended to “activate dialogue in various spheres, including strategic security.”

Sanders also said the two leaders discussed Ukraine. Trump canceled a summit meeting with Putin late last year after Russia seized three Ukrainian Navy ships on Nov. 25 and arrested 24 sailors.

Putin also told Trump that the new leadership in Ukraine should take steps to solve the Ukrainian crisis, the Kremlin said.

Trump also raised with Putin the issue of getting North Korea to dismantle its nuclear weapons and ballistic missile programs. Trump has met twice with North Korean leader Kim Jong Un but Kim has yet to agree to a disarmament deal.

Sanders said Trump mentioned several times “the need and importance of Russia stepping up and continuing to put pressure on North Korea to denuclearize.” The Kremlin said both leaders highlighted the need to pursue denuclearization of the region.

During an April summit with Kim in Vladivostok, Putin expressed Russian support for a gradual process of trading disarmament for sanctions relief.