By Joyce Lee and Jack Kim

SEOUL (Reuters) -North Korea on Tuesday said South Korea's plan to build nuclear-powered submarines with U.S. approval would trigger a "nuclear domino" effect.

On Friday, South Korea and the U.S. jointly released the details of the agreement struck by President Lee Jae Myung and President Donald Trump at their summit last month, which included a commitment to disarm the North's nuclear arsenal.

The U.S. also gave the green light for South Korea to build nuclear-powered attack submarines, a goal that had been long harboured by Seoul.

The agreement revealed the "true colours of the confrontational will of the U.S. and the ROK to remain hostile towards the DPRK," the state news agency KCNA said on Tuesday, using the acronyms for South and North Korea. That pledge and a series of large-scale joint military drills by the two countries posed grave challenges to the North's security and aggravated regional tensions, it said.

It accused Seoul of secretly advancing a "long-cherished ambition to possess nuclear weapons" that is bound to set off a "nuclear domino phenomenon" in the region and spark an arms race.

South Korea's Lee has said the submarines were critical to maintaining readiness against China's naval forces and the potentially grave threat from the nuclear-armed North's push to develop its own nuclear-powered submarines.

South Korean presidential office spokesperson Kang Yu-jung said later on Tuesday that Seoul has no hostile or confrontational intent against the North and cooperation with the U.S. was intended to protect its national security interests.

Hong Min, a North Korea expert at the Korea Institute for National Unification in Seoul, said the commentary showed the North remained unwilling to engage in dialogue with Washington as long as the U.S. did not recognize it as a nuclear state.

Trump has said he is ready to meet with North Korean leader Kim Jong Un. The pair met three times during the U.S. president's first term, aiming for a nuclear deal, but failed to reach an agreement.

(Reporting by Joyce Lee and Jack Kim; Editing by Rod Nickel, Ed Davies and Thomas Derpinghaus)