* Obama seeking to underline U.S. commitment to region
* U.S. needs to balance Japanese and Chinese concerns (Adds welcoming ceremony with emperor, Abe comment)
By Linda Sieg and Matt Spetalnick
TOKYO, April 24 (Reuters) - U.S. President Barack Obama will use a state visit to Japan on Thursday to try to reassure Asian allies of his commitment to ramping up U.S. engagement in the region, despite Chinese complaints that his real aim is to contain Beijing's rise.
Obama is being treated to a display of pomp and ceremony meant to show that the U.S.-Japan alliance, the main pillar of America's security strategy in Asia, remains solid at a time of rising tensions over growing Chinese assertiveness and North Korean nuclear threats.
U.S. and Japanese trade negotiators for the two countries were working around the clock in Tokyo on a two-way trade pact seen as crucial to a broader trans-Pacific agreement.
"We're continuing to work," a U.S. official said on Thursday, before the leaders were to meet on the first state visit to Japan by a U.S. president in 18 years.
"Autos and agriculture continue to be the focus, and our goal remains to achieve meaningful market access for American businesses, farmers and ranchers," the official said. "We've made some progress and worked around the clock."
Even if Obama and Japanese Prime Minister Shinzo Abe cannot complete a bilateral trade deal before the U.S. president leaves Tokyo on Friday, they are likely to try to project a sense of progress on key issues.
The challenge for Obama during his week-long, four-nation tour will be to convince Asian partners that Washington is serious about its promised strategic "pivot" towards the region, while at the same time not harming U.S. ties with China, the world's second-biggest economy.
The difficulty of Obama's balancing act was underscored hours before he arrived on Wednesday night when Chinese state media criticized U.S. policy in the region as "a carefully calculated scheme to cage the rapidly developing Asian giant".
The official Xinhua news agency followed that on Thursday with a commentary that said: "...the pomp and circumstance Obama receives ... cannot conceal the fact that Tokyo has become a growing liability to Washington's pursuit of long-term interests."
Obama told Japan's Yomiuri newspaper that while Washington welcomed China's peaceful rise, "our engagement with China does not and will not come at the expense of Japan or any other ally".
An Obama-Abe joint statement is likely to specify that tiny islands in the East China Sea, claimed by Beijing, are administered by Japan and fall under the U.S.-Japan treaty that obliges Washington to defend Tokyo, Japanese media said on Thursday.
This is standard U.S. policy, but putting Obama's name to such a statement would reassure Japan on an issue that is a source of tension between Asia's biggest powers.
Obama's trip will also include stops in South Korea, Malaysia and the Philippines. Leaders who will meet Obama are also keeping a wary eye on the crisis in Ukraine through the prism of their own territorial disputes with Beijing.
Some of China's neighbours worry that Obama's apparent inability to rein in Russia, which annexed Crimea last month, could send a message of weakness to China.
MESSAGE OF SOLIDARITY
The Japanese government lobbied hard to get the White House to agree to an official state visit, the first by a sitting U.S. president since Bill Clinton in 1996.
Topping Obama's schedule on Thursday was an audience with Emperor Akihito at the Imperial Palace and a summit with Abe followed by a joint news conference. He will also visit the Meiji Shrine, which honours the Japanese emperor who oversaw the country's rapid modernisation in the late 1800s.
At an official welcoming ceremony by Emperor Akihito, Obama walked smiling past Japanese schoolchildren waving small U.S. and Japanese flags, solemnly inspected a rifle-bearing military honour guard, and shook hands with Japanese dignitaries in front of the sprawling palace before heading inside with his hosts.
Abe will be trying to soothe U.S. concerns that his conservative push to recast Japan's war record with a less apologetic tone is overshadowing his pragmatic policies on the economy and security.
Obama and Abe are expected to send a message of solidarity after strains following Abe's December visit to Tokyo's Yasukuni Shrine, seen by critics as a symbol of Japan's past militarism.
"I would like to have the kind of summit meeting that will send a message to the world that security relations between Japan and the United States are firm and solid," Abe told reporters on Wednesday night after the two leaders dined at an upscale sushi restaurant.
In his remarks to the Yomiuri, Obama has already assured Japan that the bilateral defence treaty covers the disputed islets, called the Senkaku by Japan and the Diaoyu by China.
The Obama-Abe joint statement will say the two allies will not tolerate any attempt to change the status quo there by force, a phrase that implicitly targets China. (Additional reporting by Mark Felsenthal, Antoni Slodkowski and Chris Meyers; Editing by Mike Collett-White, William Mallard)