U.S. intelligence agencies assess that Russia and China will seek to interfere in the 2020 presidential election, having learned lessons from Russia's operation in 2016, according to the annual public survey of national security threats issued Tuesday.

"We assess that foreign actors will view the 2020 U.S. elections as an opportunity to advance their interests," Dan Coats, the director of national intelligence, told the Senate intelligence committee at the worldwide threats hearing.

In another notable statement, Coats noted that U.S. intelligence agencies believe North Korea is unlikely to give up its nuclear weapons because "its leaders ultimately view nuclear weapons as critical to regime survival." That view stands in stark contrast to comments from President Donald Trump, who in June declared that North Korea was "no longer a nuclear threat," citing his talks with leader Kim Jong Un.

Coats also rebutted Trump's statement that ISIS has been defeated. He said the group was "nearing" military defeat in Iraq, but has returned to its "guerrilla warfare roots," continues to plot attacks and "still commands thousands of fighters in Iraq and Syria."

On political interference, the written assessment added that intelligence analysts expect American adversaries "to refine their capabilities and add new tactics as they learn from each other's experiences, suggesting the threat landscape could look very different in 2020 and future elections."

Political interference, using social media and cyberattacks, was scarcely mentioned in threat assessments before last year, but it was listed second behind cyberattacks in Tuesday's array of the challenges facing U.S. national security policymakers.

"Russia's social media efforts will continue to focus on aggravating social and racial tensions, undermining trust in authorities, and criticizing perceived anti-Russia politicians," says the written threats assessment. "Moscow may employ additional influence toolkits — such as spreading disinformation, conducting hack-and- leak operations, or manipulating data — in a more targeted fashion to influence U.S. policy, actions and elections."

China and Iran may also seek to influence American politics, the assessment said. And China and Russia are working together as never before in recent history.

"China and Russia are more aligned than at any point since the mid-1950s, and the relationship is likely to strengthen in the coming year as some of their interests and threat perceptions converge, particularly regarding perceived U.S. unilateralism and interventionism and Western promotion of democratic values and human rights," the assessment says.

The worldwide threats hearing is generally the one time during the year that all the heads of major U.S. intelligence agencies testify in public about the threats facing the nation.

FBI Director Christopher Wray may be asked about the acting attorney general's comment Monday that the Mueller investigation is wrapping up, and he may be pressed about how much of Mueller's findings will be made public.