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By Chris Buckley

TOKYO, April 11 (Reuters) - Chinese Premier Wen Jiabao and Japanese Prime Minister Shinzo Abe agreed on Wednesday to build a "strategic" relationship, but Wen warned that disputes over the wartime past could still hurt the fragile rapprochement.

Wen's three-day visit, the first by a Chinese leader since 2000, aims to deepen a thaw begun with a trip by Abe to Beijing in October. The two sides did not achieve a breakthrough in a sea territory dispute this time, but came out of their summit promising cooperation in energy, diplomacy and security.

"In today's meeting with Premier Wen, we were able to agree to push forward many specific points of cooperation towards building a mutually beneficial strategic relationship," Abe said in a banquet speech punctuated by smiles and anecdotes.

Sino-Japanese ties grew chilly under Abe's predecessor, Junichiro Koizumi, who made annual visits to Tokyo's Yasukuni war shrine, seen in Asia as a symbol of Japan's past militarism.

"China-Japan ties are at a crucial point of inheriting the past and opening up the future," Wen said at the banquet.

He was blunter when the cameras weren't rolling.

"If we can handle the history issue well, it would be a good foundation for the development of bilateral ties," a Japanese official quoted Wen as telling Abe.

"If not, it will become an impediment to Sino-Japanese ties."

Koizumi's visits to Yasukuni, where Japanese World War Two leaders convicted as war criminals are honoured along with war dead, angered China and led it to reject bilateral summits.

Abe paid his respects at the shrine before taking office last September, but has declined to say whether he will do so as prime minister. In an interview last week, Wen pointedly pressed him not to go.

But there was no indication from China that Wen explicitly raised Yasukuni with Abe during their meeting.

Abe accepted an invitation from Wen to visit Beijing again this year, and the two sides issued documents on cooperation in energy and environmental protection, as well as a joint press release that promised more communication on defence and security concerns and high-level economic talks in Beijing this year.

The two countries' economies are already inextricably intertwined. China including Hong Kong is already Japan's biggest trade partner, ahead of the United States, with two-way trade totalling nearly 29 trillion yen ($240 billion) last year.

THORNY DISPUTES

But on one of the thorniest economic disputes -- a feud over oil and gas fields in disputed waters in the East China Sea -- the leaders agreed only to speed up talks and seek a report on ways to jointly develop the resources by autumn.

Even as they met, China's state-owned CNOOC Ltd. said it had produced gas at a field in the East China Sea last year, despite Japanese objections to development.

Beijing and Tokyo are at loggerheads over the boundary between their exclusive economic zones, and Tokyo fears Chinese development may drain off its resources.

"The East China Sea issue is an extremely complex one between China and Japan, and resolving it certainly requires time," Chinese Foreign Ministry spokesman Liu Jianchao told reporters in Tokyo after the summit.

The two East Asian powers are also suspicious of each other's military ambitions, and Abe called for greater transparency in Beijing's double-digit defence spending.

But even in military matters, the two sides offered steps to ease tensions. China and Japan should notify each other of major military activities and found a "maritime crisis management centre," Wen proposed, according to spokesman Liu.

"In security, neither side should view the other as a threat or a challenge," Wen told Abe, according to Liu.

Abe welcomed Wen's proposals and invited China's defence minister and a naval ship to visit, Liu added. Wen also invited Japan's defence minister to visit China.

North Korea was also on the agenda, with the two leaders agreeing to work together to get Pyongyang to implement a February agreement to abandon its nuclear arms programme.

China, for its part, agreed to try to help resolve Tokyo's feud with the North over Japanese citizens kidnapped decades ago.

On Thursday, Wen is to give a speech to the Japanese parliament and meet business and political leaders.

(Additional reporting by Teruaki Ueno, Chisa Fujioka, George Nishiyama and Elaine Lies)

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