China urged the United States to sack the head of the U.S. Pacific Command in return for exerting more pressure on North Korea amid concerns over its growing nuclear and missile threats, a source close to U.S.-China ties said Saturday.

The Chinese leadership headed by President Xi Jinping made the request, through its ambassador in the United States, to dismiss Adm. Harry Harris, known as a hard-liner on China, including with respect to the South China Sea issue, the source said.

China’s envoy to the United States, Cui Tiankai, conveyed the request to the U.S. side, to coincide with the first face-to-face, two-day meeting between President Donald Trump and Xi in Florida from April 6, but the Trump administration likely rejected it, the source said.

China is a longtime economic and diplomatic benefactor of North Korea.

As the head of Pacific Command, Harris, who was born in Japan and raised in the United States, plays a vital role in the security of the region.

He was responsible in ordering last month the dispatch of the USS Carl Vinson aircraft carrier to waters near off the Korean Peninsula in a show of force amid signs the North was preparing to test-fire another ballistic missile or conduct a sixth nuclear test.

The Trump administration has called for exerting “maximum pressure” on North Korea to prod it to give up its nuclear and missile programs. The administration has said all options — including a military strikes — remain on the table.

Harris has pushed for the U.S. deployment of the advanced Terminal High Altitude Area Defense (THAAD) anti-missile system to South Korea. China has opposed the deployment, saying it could undermine its security interests and the strategic balance of the region.

He has also called for continuing U.S. “freedom of navigation” operations in the contested South China Sea. Overlapping territorial claims, as well as land construction and militarization of outposts in disputed areas in the sea, remain a source of tension in the region.

According to the source, Cui also asked the Trump administration not to label China as a currency manipulator. As per the request, the United States did not label China as such, in light of Beijing’s role in helping Washington deal with the North Korean issue.