North Korea has expanded a uranium enrichment facility and restarted a plutonium reactor that could start recovering material for nuclear weapons in weeks or months, according to the US intelligence chief.

Director of National Intelligence James Clapper said US intelligence has assessed that Pyongyang has expanded the uranium enrichment facility at Yongbyon and restarted the plutonium production reactor there.Mr Clapper told the Senate Armed Services Committee that the North has been operating thereactor long enough that it could begin to recover plutonium"within a matter of weeks to months".The Yongbyon reactor was mothballed in 2007 under an aid-for-disarmament agreement, but North Korea started renovating it after its third nuclear test in 2013.When it is fully operational it is capable of producing around six kilos (13 pounds) of plutonium a year, enough for one nuclear bomb, experts say.
The findings of US intelligence will fuel concern that North Korea is making technical advances in its nuclear weapons programme and working to expand what is thought to be its small nuclear arsenal.Experts in the US have estimatedthat Pyongyang may have around 10 bombs, but that could grow to between 20 and 100 by 2020.On Sunday North Korea launcheda rocket carrying an Earth observation satellite into space.
President Barack Obama has spoken with Japanese Prime Minister Shinzo Abe and South Korean President Park Geun-Hye,and agreed on the need for a"strong and united international response to North Korea's provocations, including through a robust UN Security Council Resolution," the White House said.South Korea's Defence Ministry on Tuesday released pictures of what it said was rocket debris it found after the launch. The rocket launch followed an underground nuclear explosion in January that the North claimedwas the successful test of a"miniaturised" hydrogen bomb.This claim has prompted scepticism, and Mr Clapper said the low yield of the test "is not consistent with a successful testof a thermonuclear device".North Korea is committed to developing a long-range, nuclear-armed missile capable of posing a direct threat to the US, but Mr Clapper said "the system has notbeen flight-tested".