Cambodian Senate President Hun Sen and Chinese President Xi Jinping met on Tuesday in Beijing and agreed to boost bilateral ties. They said the countries have an "ironclad friendship."

Hun Sen was Cambodia's prime minister for nearly four decades, until last year when he handed the post to his son, Hun Manet. Hun Sen has maintained a strong influence over Cambodia since assuming the presidency of the Senate in April.

The Chinese foreign ministry said he called China his country's most trusted friend. It said their friendship won't change with intergenerational leadership transitions in Cambodia.

China is the largest investor in Cambodia. The Cambodian government said Hun Sen asked Xi for more economic support and investments.

Meanwhile, Xi expressed his opposition to external forces introducing a Cold War mentality into the region.

The two countries are apparently aiming to keep US involvement in Southeast Asia in check, ahead of the inauguration of President-elect Donald Trump.