WASHINGTON - U.S. President Barack Obama has written a personal letter to North Korean leader Kim Jong-Il amid efforts by the United States to persuade Pyongyang to return to nuclear disarmament talks.

The letter was delivered by U.S. special envoy Stephen Bosworth during his three-day trip to North Korea last week. A U.S. official confirmed the letter was sent but would not discuss its contents.

North Korea hinted last Friday following the talks with Bosworth that it could end its year-long boycott of the six-party nuclear negotiations with the United States, China, Japan, Russia and South Korea.

Bosworth's meetings capped months of manoeuvring to reduce tensions after North Korea test-fired missiles and set off a nuclear device, triggering U.N. sanctions.

Bosworth said in China after his visit that patience would be needed in seeking the resumption of the six-party talks, which are aimed at persuading Pyongyang to dismantle its nuclear weapons program.

It is relatively rare for a U.S. president to send a personal letter to the North Korean leader, though President George W. Bush sent one to Kim in December 2007. Bush's letter raised the possibility of normalized relations in exchange for North Korea's full disclosure of its nuclear programs.

(Editing by Eric Beech)