(Adds comments from Pentagon spokesman, paragraphs 4-6)
By Paul Eckert, Asia Correspondent
WASHINGTON, Feb 5 A key part of a major realignment of U.S. forces in Japan in which 8,000 Marines would be shifted from Okinawa to Guam, is likely to be delayed beyond its 2014 target date, the commander of U.S. forces in Asia and the Pacific said on Thursday.
"We are behind a timeline to achieve that goal of 8,000 (Marines) down to Guam, and we don't have enough money to make it happen right now," Navy Adm. Timothy Keating said.
"I don't think it will happen on time. I think it will be more expensive," he told Reuters in an interview.
But the Pentagon, anxious to reassure Japan of its commitment to the timetable, later took the unusual step of publicly disagreeing with Keating's assessment.
"We have no reason to believe that we are not going to meet the timeline we have set out," Pentagon press secretary Geoff Morrell said.
"He's certainly entitled to his opinion on this matter," Morrell said of Keating's statement. "But officially we are committed to the roadmap as agreed."
In the interview, Keating stressed that there had been no change under the new Obama administration to the major overhaul plan, unveiled in 2006 and formally called the Defense Policy Review Initiative.
Analysts say key elements of the plan to shift troops away from the southern Japanese island of Okinawa have been held up by wrangling between the central government and the local government on the densely populated southern island.
Okinawa plays host to the bulk of the 50,000 U.S. troops based in Japan under a bilateral treaty and islanders have chafed at military accidents and crimes such as rape committed by U.S. servicemen.
Keating played down the impact of any delay.
"A case can be made that a more measured, longer-term approach approach ... could be beneficial," he said.
"It could be reassuring to our friends and allies in the region that we're not abandoning Japan, we're not rushing to judgment," Keating said.
Guam, the largest of the Mariana Islands in the western Pacific, is a U.S. territory and is home to a number of military bases. (Editing by Eric Walsh)