North Korean leader Kim Jong Un inspects the intercontinental ballistic missile Hwasong-14 in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang, July 5, 2017. KCNA/Reuters

Seoul, South Korea -- The North Korean regime has suggested it is rethinking whether it should abide by its moratorium on nuclear and missile tests and other steps aimed at improving ties with the U.S. A statement by the Foreign Ministry on Tuesday appeared aimed at applying more pressure on the U.S. as the two countries attempt to resume nuclear diplomacy.

The statement said upcoming regular U.S.-South Korean military drills that North Korea views as an invasion rehearsal were forcing it to rethink whether it should remain committed to the promises it made to the U.S.

The North said President Trump had vowed to suspend military drills with South Korea during his first and third meetings with North Korean leader Kim Jong Un.

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The Foreign Ministry statement called a U.S. decision to go ahead with the war games would be "clearly a violation of the basic spirit" of the agreement between the two countries, and thus North Korea's impetus to adhere to its own pledges was "gradually disappearing."

The statement also said Pyongyang was not bound by any legal documents to suspend nuclear and missile tests.

Despite an historic and controversial visit paid by President Trump to North Korean territory early this month, during which he met Kim for about 45 minutes, there has been scant indication of any real headway in the diplomatic standoff between the two nations.

Mr. Trump told reporters he and Kim had agreed to restart negotiations on a deal to pave the way for the complete denuclearization of the Korean peninsula. The president, who hailed his "great relationship" with the North Korean strongman, invited Kim to the White House to continue their talks.

Thousands of U.S. forces have remained in South Korea, mostly along the heavily fortified border with the North, since open warfare ceased in the Korean War 1953. There still has not been a treaty to officially end that war.

Mr. Trump said shortly before he met Kim that it was too soon to know whether he might hold a third formal summit with Kim following an unsuccessful meeting earlier this year in Vietnam.