US Secretary of State John Kerry warned China Tuesday against any move to declare an air defence zone in the South China Sea, as he affirmed defence ties with long-time ally the Philippines.

Kerry, in Manila for a two-day visit, criticised China for its declaration last month of an Air Defence Identification Zone (ADIZ) in the East China Sea including over disputed islands.

He warned Beijing against any similar move in the South China Sea, where it has overlapping claims with several Asian countries including the Philippines.

Kerry also announced that Washington had committed $40 million to help the Philippines strengthen its sea defence capabilities.

The two sides are also in the final stages of hammering out a deal allowing more US troops, aircraft and ships to pass through the Philippines, where the last US bases closed in 1992.

"Today, I raised our deep concerns about China's announcement of an East China Sea air defence identification zone," Kerry said after meeting his Filipino counterpart Albert del Rosario.

"The zone should not be implemented and China should refrain from taking similar, unilateral actions elsewhere in the region, and particularly over the South China Sea," he told a joint news conference.

The Philippines had said last month that Beijing's announcement of its ADIZ in the East China Sea raised the prospect of it doing the same in the South China Sea.

China claims almost all the South China Sea but the Philippines, Vietnam, Malaysia, Brunei and Taiwan have overlapping claims.

Tensions between the Philippines and China have risen in recent years as Beijing becomes more aggressive in asserting its claims.

Earlier this year Manila took Beijing to a United Nations tribunal over the contested Scarborough Shoal, which has been controlled by Chinese government vessels since last year.

Beijing's East China Sea zone requires aircraft to provide flight plans when traversing the area, declare their nationality and maintain two-way radio communication, or face "emergency defensive measures".

The zone covers disputed Tokyo-controlled islands -- known as the Senkakus in Japan and the Diaoyus in China -- where ships and aircraft from the two countries already shadow each other.

"I told the (Philippine) foreign secretary that the United States does not recognise that (East China Sea) zone and does not accept it," Kerry said.

Kerry also threw his support behind the Philippines, calling it a "key treaty ally".

"The United States is committed to working with the Philippines to address its most pressing security challenges," he said.

"That is why we are negotiating a strong and enduring framework agreement that will enhance defence cooperation under our alliance, including through an increased rotational presence in the Philippines."

John Blaxland, a defence analyst at the Australian National University's College of Asia and the Pacific, earlier said Kerry's visit was meant to assure the region that America "is not just a fair-weather friend".

"Kerry's visit can be expected to act as a catalyst for change," Blaxland told AFP, and underscored the Philipines's important role as Washington embarks on its so-called pivot to Asia.

Kerry was expected to meet President Benigno Aquino Tuesday night, and visit the typhoon-ravaged central city of Tacloban Wednesday.

Kerry said the United States stood ready to assist the Philippines in the long road to rebuilding, more than a month after Super Typhoon Haiyan left more than 6,000 people dead and over four million homeless.

The United States provided massive humanitarian assistance, deploying an aircraft carrier and mobilising 1,000 Marines.

On Tuesday Kerry paid tribute to the "resilience" of the Filipino people, which he said had inspired the world.

Del Rosario said Kerry's trip underscored the "increased momentum" of bilateral and defence ties.