BEIJING: US Secretary of State John Kerry met the president and top officials of North Korea’s key ally and aid provider China on Saturday to press them to rein in a defiant Pyongyang, seeking Beijing’s help to defuse soaring nuclear tensions.

The current situation on the Korean peninsula is at a “critical time”, Kerry told President Xi Jinping as he arrived to seek Beijing’s intervention in the crisis.

“Mr President, this is obviously a critical time with some very challenging issues,” Kerry told Xi in the Great Hall of the People in Beijing. “Issues on the Korean peninsula, the challenge of Iran and nuclear weapons, Syria and the Middle East, and economies around the world that are in need of a boost.”

Beijing is Pyongyang’s sole major ally and its key provider of aid and trade, and is seen as having unique leverage over the government of Kim Jong-Un, which has issued repeated threats of nuclear war.

But Xi did not refer to the Korean peninsula in his opening remarks at the meeting, instead saying that the US-China relationship was “at a new historical stage and has got off to a good start”.

Earlier, Kerry met with China’s foreign minister Wang Yi after flying in from talks in South Korea with President Park Geun-Hye, where he offered public US support for her plans to initiate some trust-building with the North.

The Korean peninsula has been engulfed by escalating military tensions and dire threats of nuclear war ever since North Korea conducted a rocket test last December and a nuclear test in February.

“Obviously there are enormously challenging issues in front of us, and I look forward to having that conversation with you today,” Kerry told Wang.

Wang agreed the visit came at a “critical moment”.

China has backed North Korea since the 1950-53 Korean War and could wield tremendous leverage over the isolated communist regime thanks to the vital aid it provides, including almost all of its neighbour’s energy imports.

But analysts say it is wary of pushing too hard for fear of destabilising North Korea, which could send a wave of hungry refugees flooding into China and ultimately lead to a reunified Korea allied with the United States.

China and the US have a sometimes strained relationship, with Beijing uneasy over Washington’s ‘rebalancing’ towards Asia, and Kerry's first visit to the region since becoming America's top diplomat has been completely overshadowed by the Korean crisis.

Washington is seeking to persuade Beijing to help rein in the bellicose threats from North Korean leader Kim Jong-Un, and bring Pyongyang back to the negotiating table over its suspect nuclear programme.

“I think it’s clear to everybody in the world that no country in the world has as close a relationship or as significant an impact on the DPRK (North Korea) than China,” Kerry said in Seoul after meeting South Korean leaders.

China is estimated to provide as much as 90 per cent of its neighbour’s energy imports, 80 per cent of its consumer goods and 45 percent of its food, according to the US-based Council on Foreign Relations.