"There have been moves to redesignate the North (as a terror sponsor), but momentum was not created," the senior official said on background. "Due to the North's recent moves, I think the momentum (for redesignation) would be strengthened."

A House bill has already been submitted that calls for adding the North to the terrorism list, he said.

The recent killing, coupled with the North's test-firing of an intermediate-range ballistic missile earlier this month, has raised fresh calls in Congress for putting the communist regime back on to the list of states sponsoring terrorism.

On Wednesday, Sen. Cory Gardner, a leading voice in Congress for greater pressure on Pyongyang, called for the North's redesignation, telling Yonhap News Agency that the murder "is yet another reminder of North Korea's brutality."

The North was put on the US terrorism sponsor list for its 1987 midair bombing of a Korean Airlines flight that killed all 115 people aboard. But the US administration of former President George W. Bush removed Pyongyang from the list in 2008 in exchange for progress in denuclearization talks.

Last month, Rep. Ted Poe introduced a bill in the House of Representatives calling for adding the North to the terrorism list. The legislation was referred last week to the Subcommittee on Asia and the Pacific, and the Subcommittee on Terrorism, Nonproliferation, and Trade. (Yonhap)