* Kerry: U.S. "neither recognizes nor accepts" China zone
* No mention made of visit to controversial war shrine
* Japanese minister says Tokyo will work on South Korea ties
* China says Kerry remarks on air zone "irresponsible" (Adds Chinese foreign ministry response on Saturday)
WASHINGTON, Feb 7 (Reuters) - The United States on Friday stressed its commitment to the defense of Japan and stability in the Asia-Pacific region against a backdrop of increasingly assertive territorial claims by China.
After a meeting with Japanese Foreign Minister Fumio Kishida, Secretary of State John Kerry emphasized the importance of the U.S.-Japan relationship, which both countries say remains robust in spite of a bump after Japanese Prime Minister Shinzo Abe visited a controversial war shrine in December.
Kerry said the United States and Japan were committed to closer security collaboration and stressed the long-standing U.S. commitment to defend Japan if it is attacked.
"I ... underscored that the United States remains as committed as ever to upholding our treaty obligations with our Japanese allies," Kerry told reporters after talks with Kishida.
"That includes with respect to the East China Sea," Kerry said. He reiterated that Washington "neither recognizes nor accepts" an air-defense zone China has declared in the region that it disputes with Japan and other Asia nations. Kerry also said the United States would not change how it conducts operations there.
"We are deeply committed to maintaining the prosperity and the stability in the Asia-Pacific," Kerry said.
The United States flew B-52 bombers through the Chinese air defense zone after it was declared last year. U.S. officials have warned that any declaration by Beijing of another such zone in the South China Sea could result in changes to U.S. military deployments in the region.
China's foreign ministry spokesman, Hong Lei, attacked Kerry's remarks in a statement on Saturday, saying China's air-defense zone was fully in line with international law and norms.
"We urge the U.S. side to stop making irresponsible remarks so as not to harm regional stability and the China-U.S. relationship," Hong said.
In a separate statement Hong also said that any policy adjustment by the United States in the Asia-Pacific region "must work for regional peace and stability."
He was responding to remarks in a Feb. 4 briefing in Washington by Daniel Russel, State Department assistant secretary for East Asian and Pacific affairs, that the U.S. plans to intensify efforts to rebalance its policy in the Asia-Pacific region.
Kerry said he planned to visit China and other Asia countries next week.
Kishida's Washington visit comes at a time of growing concerns in Tokyo as to the long-term ability and willingness of the United States to defend Japan in spite of President Barack Obama's stated policy of rebalancing America's military and economic focus toward Asia in response to China's growing clout.
Such concerns have added momentum to Abe's drive to beef up Japan's air and naval forces while loosening constitutional limits on action that its military can take abroad.
After an agreement drawn up by Kerry and Kishida and their countries' defense ministers last year, the allies have begun revising guidelines on defense cooperation last updated in 1997, aiming to complete a revamp by the end of this year.
Washington has long encouraged Tokyo to take a greater share of the bilateral security burden, but U.S. officials have not made clear if they want Japan to acquire greater offensive capability.
Kerry made no mention of Abe's controversial visit to Tokyo's Yasukuni war shrine, which prompted an expression of disappointment from Washington and chilled Tokyo's often thorny ties with the other key U.S. ally in North Asia, South Korea.
Kishida said there were "difficult issues" between Tokyo and Seoul, but pledged to try to improve ties.
"The Republic of Korea is an important neighbor for Japan, so going forward, we will make tenacious efforts to build our cooperative relationship with the Republic of Korea from a broad perspective," he told the joint briefing with Kerry.
Amid competing claims by Seoul and Tokyo for Obama's time during a planned visit to Asia in April, Kishida said the U.S. president was being invited for a state visit.
According to Japanese media, officials in Tokyo hope the ceremonial aspect of such a visit, rather than an official or working trip, would emphasize the importance of the U.S.-Japan alliance and ease the mood over Abe's shrine visit.
Kerry and Kishida emphasized the importance of the Trans-Pacific Partnership (TPP), a multilateral trade pact Obama has been hoping can be concluded by the time of his Asia trip.
Prospects for that have dimmed due to opposition from within Obama's own Democratic Party to granting him fast-track Trade Promotion Authority given concerns that the TPP could cost American jobs. (Additional reporting by Matt Spetalnick and Jonathan Standing in Beijing; Editing by Will Dunham, Dan Grebler and Richard Borsuk)