N.Korea casts doubt on Trump summit, suspends talks with South

* N.Korea says U.S.-S.Korea drills threaten prospects for summit

* W.House says no information from N.Korea about cancelling summit

* N.Korea cancels planned meeting with S.Korea at DMZ

* South says postponed inter-Korean meeting 'regrettable' (Adds S.Korea reaction, defence ministry comment, paragraphs 3, 20-21)

By Josh Smith

SEOUL, May 16 (Reuters) - North Korea threw into question next month's unprecedented summit between Kim Jong Un and U.S. President Donald Trump, denouncing on Wednesday U.S.-South Korean military exercises as a provocation and calling off high-level talks with Seoul.

A report on North Korea's official KCNA angrily attacked the "Max Thunder" air combat drills, which it said involved U.S. stealth fighters and B-52 bombers, and appeared to mark a break in months of warming ties between North and South Korea and between Pyongyang and Washington.

The "Max Thunder" drills, aimed at "boosting the capability of pilots", would go on as planned and were not aimed at attacking a third party, the South's defence ministry said.

Any cancellation of the June 12 summit in Singapore, the first meeting between a serving U.S. president and a North Korean leader, would deal a major blow to Trump’s efforts to score the biggest diplomatic achievement of his presidency.

Trump has raised expectations for a successful meeting even as many analysts have been sceptical of the chances of bridging the gap due to questions about North Korea's willingness to give up a nuclear arsenal that it says can hit the United States.

The KCNA report called the air drills a "provocation" that went against the trend of warming ties.

"This exercise, targeting us, which is being carried out across South Korea, is a flagrant challenge to the Panmunjom Declaration and an intentional military provocation running counter to the positive political development on the Korean Peninsula," KCNA said, referring to a joint statement from an April 27 inter-Korea summit.

"The United States will also have to undertake careful deliberations about the fate of the planned North Korea-U.S. summit in light of this provocative military ruckus jointly conducted with the South Korean authorities," KCNA said.

WARMING TIES

A Trump-Kim summit until recently had looked impossible given the insults and threats the two leaders exchanged last year over North Korea's development of nuclear missiles capable of hitting the United States.

"Kim Jong Un had said previously that he understands the need and the utility of the United States and the Republic of Korea continuing in its joint exercises," U.S. State Department spokeswoman Heather Nauert told a briefing.