Former senior U.S. officials and academics met with North Korea's chief nuclear negotiator in Singapore Sunday to talk about the country's nuclear weapons buildup.

The U.S. and North Korea do not have formal diplomatic relations, but former U.S. officials occasionally meet diplomats from the North to try and settle the impasse over the country's pursuit of a long-range nuclear-armed missile that could hit the U.S. mainland.

Leon Sigal, director of the Northeast Asia Cooperative Security Project at the Social Science Research Council, a U.S.-based nonprofit, told reporters that the meeting will cover the North's nuclear missile programs. He said "it's two ways of taking each other's temperature."

The North's side was led by Ri Yong Ho, the chief negotiator for six-party denuclearization talks.

The isolated country has indicated willingness to resume the stalled talks, but has not taken concrete steps to show it remains committed to the denuclearization goal.

Earlier this month, North Korea told the United States that it is willing to impose a temporary moratorium on its nuclear tests if Washington scraps planned military drills with South Korea this year. Washington called the linking of the military drills with a possible nuclear test "an implicit threat," but said it was open to dialogue with North Korea.

Pyongyang is thought to have a handful of crude nuclear bombs and has conducted three nuclear tests since 2006. But experts are divided on how far the opaque government has come in the technology needed to miniaturize a warhead.

Sigal did not think the two sides would discuss the Sony hack after the U.S. blamed the North for the crippling cyberattack. The U.S. imposed new sanctions on the country soon after, though Pyongyang denies responsibility.

The Associated Press contributed to this report