WASHINGTON, DC (AFP) - A top United States (US) senator headed on Monday to meet senior leaders in China, Japan, South Korea and Taiwan as Congress looks for new security and trade moves in Asia.

Mr Robert Menendez, chairman of the Senate Foreign Relations Committee, will meet Japanese Prime Minister Shinzo Abe and South Korean President Park Geun Hye, along with officials in China and Taiwan, his office said.

His trip comes at a time of uneasy relations between South Korea and Japan - US allies where together more than 80,000 American troops are stationed - due to renewed disputes linked to wartime history.

Japan's ties with China have also been tense, with Mr Abe vowing a firm line against what he sees as increasingly assertive attempts by Beijing to challenge Tokyo's control over strategic islands.

Mr Abe, newly emboldened by an election victory, has advocated greater military cooperation with the US and generally supported a plan to move the controversial Futenma air base within crowded Okinawa island.

The US Congress has held up a 2006 Futenma relocation plan due partly to an earlier political backlash in Japan as well as concerns over rising costs of relocating Marines to Guam.

On Taiwan, US lawmakers including Mr Menendez, a member of President Barack Obama's Democratic Party, have supported the island's bid to buy new F-16 fighter-jets to close a military gap with Beijing.

But the Obama administration has held off on authorising the sale, a move that would trigger fierce criticism in China, which claims Taiwan.

Administration officials rarely visit Taiwan as the US does not recognise it as a country, leading the self-ruling island to court members of Congress.

Mr Obama has led a "pivot" or rebalancing toward Asia, saying US interests will increasingly be linked to the fast-growing continent, although some analysts and diplomats say its momentum has faded in his second term.