U.S. Asia experts who served in past Republican administrations said on Monday they would back Hillary Clinton in the presidential race, as a Donald Trump presidency would lead to "ruinous marginalization" for the United States in the region.

In an open letter, the eight former senior officials said that with global strategic competition growing, including from China, it was "absolutely the wrong time to elect an unstable, ill-prepared amateur with no vision or foresight to meet the manifold challenges of the 21st century."

They said the Republican nominee offered "only bluster or preposterous panaceas" for Asia that would "wreck our country's credibility, economy, and leadership in very short order."