WASHINGTON - Director of National Intelligence (DNI) Dan Coats says Russia and China present the most serious espionage and cyberattack threats to the United States as the two seek to expand their global reach.

In testimony on worldwide threats, Coats told the Senate on January 29 that the Kremlin's relationship with Beijing "is closer than it's been in many decades" and posed an even bigger threat as some allies pull away from Washington in reaction to changing U.S. policies on security and trade.

"China, Russia, Iran, and North Korea increasingly use cyberoperations to threaten both minds and machines in an expanding number of ways -- to steal information, to influence our citizens, or to disrupt critical infrastructure," Coats said.

Coats also said it was likely that U.S. adversaries are already looking into ways to interfere in the 2020 U.S. election, refining their capabilities and adding new tactics that may look to ratchet up social and racial tensions in the United States, undermining trust in authorities and criticizing politicians seen as anti-Russia.

In a contradiction to claims by President Donald Trump, Coats told the Senate committee that North Korea was unlikely to honor its pledges to denuclearize.

Coats noted in the newly released annual Worldwide Threat Assessment from the Directorate of National Intelligence that Pyongyang had "reversibly dismantled" parts of its infrastructure for weapons of mass destruction.

"Our assessment is bolstered by our observations of some activity that is inconsistent with full denuclearization," Coats said.

The White House has said Trump will hold a second summit with North Korean leader Kim Jong Un near the end of next month.

A landmark June summit between Trump and Kim in Singapore ended with a promise by the North Korean leader to work toward the complete denuclearization of the divided Korean Peninsula.

But intelligence sources have said that progress on the ground since the meeting has been disappointing.

Coats also warned that the Islamic State (IS) group maintains a force of thousands of fighters who pose a serious threat in the Middle East.

Coats added that IS, which once held large swaths of territory in Syria and Iraq but is now reduced to a shrinking enclave, would exploit any reduction in counterterrorism pressure to stage a comeback.

IS "still commands thousands of fighters in Iraq and Syria, and it maintains eight branches, more than a dozen networks, and thousands of dispersed supporters around the world, despite significant leadership and territorial losses," Coats said.

Trump last month announced he was ordering a full withdrawal of the 2,000 U.S. troops from Syria.

The Pentagon said it had begun the withdrawal, although how long it would take remained uncertain.