BEIJING (REUTERS) - China is serious about wanting a peaceful resolution to the bitter dispute over the South China Sea, Premier Li Keqiang told Southeast Asian leaders on Tuesday, but he signalled it was in no rush to sign a long-mooted accord.

After years of resisting efforts by the 10-member Asean to start talks on an agreement on maritime rules governing behaviour in the region, the so-called Code of Conduct, China has said it would host talks between senior officials this month.

Friction over the South China Sea, one of the world's most important waterways, has surged as China uses its growing naval might to assert its vast claims over the oil-and gas-rich sea more forcefully, raising fears of a military clash.

Four Asean nations, including Vietnam and the Philippines, have overlapping claims with China.

Taiwan also claims parts of the sea and its numerous islets.

China and the Philippines accuse each other of violating the Declaration of Conduct (DoC), a non-binding confidence-building agreement on maritime conduct signed by China and Asean in 2002.

Separately to Li's comments, Philippines Defence Secretary Voltaire Gazmin accused China of violating the informal DoC by building new structures in the Scarborough Shoal, part of the area disputed by Beijing and Manila.

"We have ... sighted concrete blocks inside the shoal which are a prelude to construction," Gazmin told a congressional budget hearing in Manila, displaying air surveillance photos of the group of rocks in the South China Sea.

He said the photos were taken on Saturday, describing them as a worrying pattern of construction that would be similar to the building of a garrison on Mischief Reef in the late 1990s.

Li, speaking at the opening of a China-Asean trade fair in the southern Chinese city of Nanning, said China had always advocated talks on the dispute on the basis of "respecting historical reality and international law".

"The Chinese government is willing and ready to assume a policy of seeking an appropriate resolution through friendly consultations," Li told the audience, which included Vietnamese Prime Minister Nguyen Tan Dung and Thai Prime Minister Yingluck Shinawatra.

China would "proceed systematically and soundly push forward talks on the Code of Conduct for the South China Sea", Li said without elaborating in comments aired live on state television.

He also repeated that talks on the dispute should only be carried out between the parties directly concerned, Beijing's standard line which rejects the involvement of outside parties such as the United States or multilateral forums.

Washington has not taken sides, but Secretary of State John Kerry reiterated in Brunei in July the US strategic interest in freedom of navigation through the busy sea and its desire to see a Code of Conduct signed quickly.

Differences such as those between China and the Philippines could be another obstacle to agreeing on a more comprehensive pact because China has stressed that countries must first show good faith by abiding by the DoC.

Critics say China is intent on cementing its claims over the sea through its superior and growing naval might, and has little interest in rushing to agree to a code of conduct.

Divisions among Asean over the maritime dispute burst into the open a year ago when a summit chaired by Chinese ally Cambodia failed to issue a closing communique for the first time in the group's 45-year history.