WASHINGTON -- A cautious U.S. President Donald Trump spoke of possible progress Tuesday after South Korea announced that North Korea would halt nuclear weapons and missile tests and put its entire atomic arsenal up for discussion if the U.S. agrees to enter a negotiation. It could also be "false hope," the American leader said.

Trump credited all sides with a "serious effort" as U.S.-allied South Korean envoys returned home from a rare visit to their northern neighbour with the news of an inter-Korean summit planned for late April. But given the North's long history of broken promises on a nuclear program that now threatens the U.S. mainland, it wasn't surprising that Trump hedged.

"Possible progress being made in talks with North Korea. For the first time in many years, a serious effort is being made by all parties concerned," "The World is watching and waiting! May be false hope, but the U.S. is ready to go hard in either direction!"

North Korea has yet to confirm details of the announcements from Seoul that appeared to open the door to dialogue between Washington and Pyongyang after a year of escalating threats by Trump and North Korean leader Kim Jong Un, and escalating fears of war.

While the offer of talks could ease tensions, the adversaries will still have to overcome deep mutual suspicion. The U.S. has consistently demanded North Korea give up its nukes, which the reclusive socialist state had previously insisted was off the table until Washington abandoned its "hostile policy" toward it. At a minimum, the Americans wanted a halt in nuclear and missile testing for talks to begin.

"Maybe this is a breakthrough. I seriously doubt it," Dan Coats, the director of national intelligence, told a Senate hearing Tuesday. He said his doubts are grounded in what he called failed efforts by previous U.S. administrations to negotiate with North Korea over its nuclear program.

Coats said Kim is "very calculating" and views his nuclear capabilities as "essential to his well-being as well as the well-being of his nation."

Since taking office, Trump has championed a policy of "maximum pressure" on North Korea, cranking up international sanctions to limit the country's trade. The North's commerce with China, its main trading partner, appears to have plummeted in recent months. The U.S. has said the pressure is designed to force North Korea to negotiate on giving up its nukes, but Trump hasn't ruled out military action.

Vice-President Mike Pence said the U.S. would remain "firm in our resolve" whichever direction talks with North Korea go. "All options are on the table and our posture toward the regime will not change until we see credible, verifiable and concrete steps toward denuclearization," Pence said in a statement.

Diplomatic prospects had appeared bleak until a flurry of interactions between the two Koreas that sealed their joint participation in last month's Winter Olympics in South Korea, and a rare visit by Kim's sister to the country. The momentum has continued since then. The high-level South Korean delegation that visited Pyongyang this week was the first to meet Kim since he took power after his dictator father's death in late 2011.

Tuesday's announcements were the most promising indication that the U.S. and North Korea could now talk.

On returning from Pyongyang, Chung Eui-yong, South Korea's presidential national security director, said North Korea expressed willingness to hold a "candid dialogue" with the United States to discuss its nuclear disarmament and establish diplomatic relations. Chung said North Korea "made it clear that it won't resume strategic provocations like additional nuclear tests or test-launches of ballistic missiles" while such talks are underway.

North Korea also said it would not need to keep its nuclear weapons if the U.S. drops its military threats and provides a credible security guarantee, Chung said. That reflects a longstanding demand from North Korea, which opposes the presence of nearly 30,000 U.S. forces in South Korea. Chung said the North promised not to use its nuclear and conventional weapons against South Korea.

Chung said he will soon fly to the United States to brief officials about the outcome of the talks with North Korea.

If U.S.-North Korean talks do start, a likely first step would be exploratory discussions to see if a serious nuclear negotiation is possible. The last such dialogue happened in 2012 and collapsed weeks after a provisional deal on a nuclear freeze was reached.

Arms control advocates said the developments greatly improve the prospects for peace and security in the region. Daryl Kimball, executive director of the U.S.-based Arms Control Association, urged the Trump administration and Congress to support "this important diplomatic opening."

But the administration will have difficult questions of its own as it gauges North Korea's intentions. An initial hurdle could be presented by U.S.-South Korean military drills that were postponed during the Olympics and are due to resume next month. North Korea is likely to push for a suspension of the drills which it views as a provocation and a threat, and may ask for relief from U.S.-led economic sanctions.

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Associated Press writer Robert Burns contributed to this report.

Since taking office, Trump has championed a policy of "maximum pressure" on North Korea, cranking up international sanctions to limit the country's trade. The North's commerce with China, its main trading partner, appears to have plummeted in recent months. The U.S. has said the pressure is designed to force North Korea to negotiate on giving up its nukes, but Trump hasn't ruled out military action.

Diplomatic prospects had appeared bleak until a flurry of interactions between the two Koreas that sealed their joint participation in last month's Winter Olympics in South Korea, and a rare visit by Kim's sister to the country. The momentum has continued since then. The high-level South Korean delegation that visited Pyongyang this week was the first to meet Kim since he took power after his dictator father's death in late 2011.

Tuesday's announcements were the most promising indication that the U.S. and North Korea could now talk.

On returning from Pyongyang, Chung Eui-yong, South Korea's presidential national security director, said North Korea expressed willingness to hold a "candid dialogue" with the United States to discuss its nuclear disarmament and establish diplomatic relations. Chung said North Korea "made it clear that it won't resume strategic provocations like additional nuclear tests or test-launches of ballistic missiles" while such talks are underway.

North Korea also said it would not need to keep its nuclear weapons if the U.S. drops its military threats and provides a credible security guarantee, Chung said. That reflects a longstanding demand from North Korea, which opposes the presence of nearly 30,000 U.S. forces in South Korea. Chung said the North promised not to use its nuclear and conventional weapons against South Korea.

If U.S.-North Korean talks do start, a likely first step would be exploratory discussions to see if a serious nuclear negotiation is possible. The last such dialogue happened in 2012 and collapsed weeks after a provisional deal on a nuclear freeze was reached.

Arms control advocates said the developments greatly improve the prospects for peace and security in the region. Daryl Kimball, executive director of the U.S.-based Arms Control Association, urged the Trump administration and Congress to support "this important diplomatic opening."

But the administration will have difficult questions of its own as it gauges North Korea's intentions. An initial hurdle could be presented by U.S.-South Korean military drills that were postponed during the Olympics and are due to resume next month. North Korea is likely to push for a suspension of the drills which it views as a provocation and a threat, and may ask for relief from U.S.-led economic sanctions.