U.S. President Donald Trump and Russian President Vladimir Putin agreed Monday to strengthen bilateral cooperation on reducing the two countries' stockpiles of nuclear arms and stopping North Korea's nuclear weapons development.

Speaking at a joint news conference after their meeting in Helsinki, Trump said he provided Putin with an update on his summit with North Korean leader Kim Jong Un last month, and that Russia wants "very much to end that problem, going to work with us. And I appreciate that commitment."

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Putin said through an interpreter, "We are glad that the Korean Peninsula issue is starting to resolve," and praised Trump's personal engagement in opting for "dialogue instead of confrontation."

Putin also said it is crucial that Washington and Moscow step up cooperation in ensuring strategic stability, global security and nonproliferation of weapons of mass destruction.

Such an initiative would include an extension of the Treaty between the United States of America and the Russian Federation on Measures for the Further Reduction and Limitation of Strategic Offensive Arms, also known as the New START Treaty, which is set to expire in February 2021 unless both sides agree to extend it.

"We believe it necessary to work together further on -- to interact on the disarmament agenda, military and technical cooperation," Putin said.

Putin expressed concern about the U.S. withdrawal from the 2015 Iran nuclear deal in May, while Trump condemned Russia's annexation of Ukraine's Crimea region in 2014 as "illegal."

Putin reiterated his denial of Russian interference in the 2016 U.S. presidential election in Trump's favor.

"The Russian state has never interfered and is not going to interfere into internal American affairs, including (the) election process," he said.

Trump claimed there was "zero collusion" between his campaign and Russia during the election, and denounced a U.S. investigation into Moscow's alleged meddling as "ridiculous."

"It has had a negative impact upon the relationship of the two largest nuclear powers in the world," he said. "We have 90 percent of nuclear power between the two countries."

"It's ridiculous what's going on with the probe," Trump said.

On Friday, the U.S. Justice Department announced the indictment of 12 Russian military intelligence officers on charges of hacking into computers of the Democratic National Committee, Hillary Clinton's campaign and other entities in an attempt to damage the Democratic presidential nominee.