DETROIT (Reuters) - A U.S. judge on Thursday refused to delay the scheduled October start of the trial of a Nigerian man charged with attempting to blow up a passenger airliner on Christmas Day 2009 with a bomb in his underwear.

Umar Farouk Abdulmutallab, 24, is charged with trying to detonate the device on a Northwest Airlines flight as it approached Detroit from Amsterdam, a scare that prompted U.S. authorities to quickly ramp up aviation security.

"This incident for which Mr. Abdulmutallab was charged occurred almost two years ago," U.S. District Judge Nancy Edmunds said in declining to change the October 4 start date of the trial.

Also on Thursday, Abdulmutallab reiterated his desire to represent himself, indicating he might speak for himself in the trial's opening and closing statements. Opening remarks are set for October 11.

Abdulmutallab previously told U.S. investigators he had received the bomb, which failed to detonate fully, and training from al Qaeda militants in Yemen, U.S. officials have said.

After the attempted attack, the Obama administration moved to strengthen U.S. airline security by deploying full-body scanners to try to detect explosives that could be hidden in a passenger's clothing.

U.S. authorities on Wednesday said they are now also on alert because new intelligence suggested that militants may try to detonate a bomb surgically implanted inside a passenger aboard an aircraft.

The case is USA v Abdulmutallab, 2:10-cr-20005, U.S. District Court for the Eastern District of Michigan.

(Reporting by Ben Klayman in Detroit; Editing by Eric Walsh)