A dozen conservative U.S. lawmakers said Wednesday they have sent a letter to Secretary of State John Kerry calling for the re-designation of North Korea as a state that sponsors terrorism.

They cited what they say is the cooperation by Pyongyang with Iran, Syria, Hezbollah and other terrorist organizations, a widespread allegation that has not yet been formally confirmed.

"North Korea is directly responsible for several international acts of terror, and it continues to maintain close ties with other State Sponsors of Terrorism (SST) listed regimes such as Iran and Syria," read the letter delivered to Kerry last week.

It was signed by Reps. Ileana Ros-Lehtinen (R-FL), Ted Poe (R-TX),  Steve Chabot (R-OH), and nine other Republican members of the House.

North Korea "continues to share equipment, technology, expertise, and knowledge with Iran and Syria in their pursuit of WMDs, ballistic missiles, and nuclear capabilities," they said.

WMDs stands for weapons of mass destruction.

Among several reasons for their request, the lawmakers pointed out that Pyongyang carried out an artillery attack against a South Korean border island in 2010, killing two civilians and two marines.

The U.S. designated North Korea as a terrorism-sponsoring state after a mid-air bombing in 1987 by the communist nation's agents of a Korean Air passenger jet.

Washington removed Pyongyang from the list in 2008 after some progress in nuclear talks.

"Administration after administration, our approach to the North Korean regime has failed," the lawmakers said in the letter. "This regime has actively opposed U.S. interests and undermined our national security, and it was a mistake to remove North Korea from the SST list." (Yonhap News)