SEOUL, South Korea — North Korea has started rebuilding the facilities it uses to launch satellites into orbit and test engines and other technologies for its intercontinental ballistic missile program, according to American military analysts and South Korean intelligence officials.

The revelation comes days after the breakdown of the second summit meeting between the North’s leader, Kim Jong-un, and President Trump last week in Hanoi, Vietnam. It could be a first sign that North Korea is preparing to end its moratorium on missile tests, which Mr. Trump has claimed as a major diplomatic achievement.

North Korea began dismantling the Sohae Satellite Launching Station in Tongchang-ri near its northwestern border with China last summer, after Mr. Kim held his first meeting with Mr. Trump in June in Singapore. It partially took down an engine test site, a rocket launchpad and a rail-mounted building used by engineers to assemble launch vehicles and move them to the launchpad.

The North did not completely dismantle the facilities, and when Mr. Kim met with President Moon Jae-in of South Korea in September, he offered to destroy them in the presence of American experts.