(Recasts with details, background)
TOKYO, June 25 (Reuters) - U.S. President Donald Trump on Tuesday reassured Japan he was committed to a military treaty that both nations have described as a cornerstone of security in Asia, after a media report said he had spoken privately about withdrawing from the pact.
Citing unidentified sources, Bloomberg reported on Monday that Trump had discussed ending the pact which he believed is one-sided because it obligated the United States to defend Japan if attacked but did not require Tokyo to respond in kind.
The report said Trump was also unhappy with plans to relocate the U.S. base on Japan's Okinawa island.
"The thing reported in the media you mentioned does not exist," chief government spokesman Yoshihide Suga told reporters in Tokyo when asked about the report.
"We have received confirmation from the U.S. president it is incompatible with the U.S. government policy," he added.
Under the security agreement, the United States has committed to defend Japan, which renounced the right to wage war after its defeat in World War Two.
Japan in return provides military bases that Washington uses to project power deep into Asia, including the biggest concentration of U.S. Marines outside the United States on Okinawa, and the forward deployment of an aircraft carrier strike group at the Yokosuka naval base near Tokyo.
Ending the pact, which also puts Japan under the U.S. nuclear umbrella, could force Washington to withdraw a major portion of its military forces from Asia at a time when China's military power is growing.
It would also force Japan to seek new alliances in the region and bolster its own defences, which in turn could raise concern about nuclear proliferation in the already tense region.
Washington's close ties to Tokyo have also benefited U.S. military contractors such as Lockheed Martin Corp and Raytheon Co, which have sold billions of dollars of equipment to Japan's Self Defense Forces.
On a visit to Japan in May, Trump said he expected Japan's military to reinforce U.S. forces throughout Asia and elsewhere as Tokyo bolsters the ability of its forces to operate further from its shores.
Part of that military upgrade includes a commitment by Japan to buy 97 F-35 stealth fighters, including some short take-off and vertical landing (STOVL)B variants worth more than $8 billion.
Japan says it eventually wants to field a force of around 150 of the advanced fighter jets, the biggest outside the U.S. military, as it tries to keep ahead of China's advances in military technology. (Reporting by Kiyoshi Takenaka; writing by Tim Kelly; editing by Darren Schuettler)