U.S. Defense Secretary Jim Mattis is expected to press for greater cooperation to contain North Korea¡¯s nuclear and missile threat at a regional security forum in Singapore later this week, where for years Washington has sought to spotlight China¡¯s expansion in the strategic South China Sea.

President Donald Trump has actively courted Chinese support on North Korea and abandoned an Asia-Pacific trade pact soon after taking office in January. That has raised concerns among Southeast Asian allies in the lead up to the annual Shangri-la dialogue starting on Friday that Washington might allow China a freer rein elsewhere in the region.

A U.S. Navy challenge to China¡¯s South China Sea claims last week may have allayed some of the concerns over broader American engagement. But Asian officials and diplomats are still hoping for a clearer articulation of Trump¡¯s policy when Mattis speaks in Singapore on Saturday.