The United States decided to leave out North Korea from its state sponsor of terrorism list released Thursday. American lawmakers introduced a bill last month proposing that the reclusive state be relisted as a sponsor of terrorism.

In its Country Reports on Terrorism 2015, the U.S. Department of State said North Korea “is not known to have sponsored any terrorist acts since the bombing of a Korean Airlines flight in 1987.” The May 19 bill, submitted to the U.S. House of Representatives, detailed over 20 cases linking North Korea with possible terrorist acts.

“In May, the United States recertified North Korea as a country ‘not cooperating fully’ with U.S. counterterrorism efforts pursuant to Section 40A of the Arms Export and Control Act, as amended. In making this annual determination, the Department of State reviewed the DPRK’s [Democratic People’s Republic of Korea, North Korea’s official name] overall level of cooperation with U.S. efforts to counter terrorism, taking into account U.S. counterterrorism objectives with the DPRK and a realistic assessment of DPRK capabilities,”  according to the state terrorism report.

Kim Jong Un North Korean leader Kim Jong Un gives field guidance to the construction site of a medical oxygen factory in this undated photo released by North Korea's Korean Central News Agency, May 30, 2016. Photo: REUTERS/KCNA

Pyongyang was designated a state sponsor of terrorism on Jan. 20, 1988, after North Korean agents bombed Korean Air Flight 858 in 1987, killing all 115 people aboard. However, in 2008, then President George W. Bush’s administration removed North Korea from the list after the East Asian country agreed to dismantle its nuclear weapons program.

The Kim Jong Un-led regime has conducted a series of missile and nuclear tests since the beginning of this year, and the leader has called for a strengthening of the country’s defense capabilities. Pyongyang also claims to have secured intercontinental ballistic missile technologies. The country faces strict sanctions from the United Nations Security Council over its fourth nuclear test in January and a rocket launch in February.

The terrorism report listed Iran, Sudan and Syria as state sponsors of terrorism. Cuba was removed from the list after the restoration of full diplomatic relations with the U.S. earlier this year.