Days after a long-range missile launch, North Korea has restarted one of its nuclear reactors and "within weeks" could begin gathering plutonium, which can be used to fuel nuclear weapons, U.S. Director of National Intelligence James Clapper said Tuesday.

Speaking to lawmakers in the intelligence community's annual Worldwide Threat Assessment, Clapper said that North Korea followed through with a 2013 promise to refurbish and restart its Yongbyon nuclear complex, which includes a uranium enrichment facility and a graphite-moderated plutonium production reactor capable of producing 13.2 pounds of plutonium per year, a U.S. official told Reuters.

"We assess that North Korea has followed through on its announcement by expanding its Yongbyon enrichment facility and restarting the plutonium production reactor," Clapper said, according to BBC.

Yongbyon was shut down in 2007 in exchange for 50,000 tons of heavy fuel promised as part of a six-nation agreement. But North Korea vowed to bring the facility back to life in March 2013 after the United Nations imposed fresh sanctions over its third nuclear test. Last September, North Korea said its main Yongbyon nuclear facility was fully operational again.

Clapper said that Pyongyang continues to expand the size and sophistication of its ballistic missile program and is "committed to developing a long-range, nuclear-armed missile that's capable of posing a direct threat to the United States - although the system has not been flight-tested," according to The Washington Times.

North Korea conducted its fourth nuclear test last month and on Saturday used a long-range rocket to launch a satellite into space, violating numerous U.N. sanctions and sparking condemnation from the U.S., its allies and the U.N. Security Council, as HNGN previously reported. North Korea insists the launch was peaceful and meant to improve its space exploration program, but the U.S. and its allies believe it was a covert test of banned ballistic missile technology. The U.N. Security Council vowed new sanctions and the U.S. Senate is scheduled to vote on sanction legislation on Wednesday.