The United States president, Donald Trump, will miss November's gathering of Asian leaders in Papua New Guinea.
Mr Trump will instead send Vice President Mike Pence to the Asia Pacific Economic Cooperation (APEC) forum.
The meeting is one of the largest gatherings of leaders from 21 countries around the Asia-Pacific rim, including the US, China, Russia, Australia and New Zealand.
Papua New Guinea, APEC's smallest member, is hosting the meeting for the first time, and has poured millions of dollars into preparations, including building a new conference centre and highways.
But critics said that had come at the expense of basic services, such as its struggling health and education systems.
Mr Trump was invited to attend the US-Association of Southeast Asian Nations summit and the East Asia summit in Singapore, as well as the APEC forum. He attended these events last November, but has asked Mr Pence to attend all three this year.
White House spokesperson Sarah Sanders said at the summits, Mr Pence would "highlight the United States' vision of a free and open Indo-Pacific, based on respect for sovereignty, the rule of law, and the principles of free, fair and reciprocal trade".
Mr Trump's decision to skip the Asian summits will inevitably raise questions about the extent of his commitment to a region that is home to some of the most pressing US foreign policy challenges.
These include Mr Trump's stalled efforts to persuade North Korea to give up its nuclear weapons programme and strategic rivalry with China, with which Mr Trump has engaged in a major trade war.
The Trump administration has touted an Indo-Pacific strategy aimed at increasing regional cooperation, notably with India, Australia and Japan, to counter China's influence, including in the disputed South China Sea, where Washington has mounted naval patrols to challenge what it sees as Beijing's excessive territorial claims.
In August, US Secretary of State Mike Pompeo attended a regional foreign ministers' meeting in Singapore to prepare for the November summits and pledged nearly $300 million in new security funding for the Indo-Pacific - a drop in the ocean compared to the billions China has been pouring into the region.
Asia experts were not surprised by Mr Trump's decision not to attend the summits.
"Trump hates traveling outside the U.S. and dislikes multilateral meetings," said Bonnie Glaser of Washington's Center for Strategic and International Studies.
Jonathan Pollack of the Brookings Institution think tank, said many in Southeast Asia see the region caught uncomfortably between the United States and China.
"The Trump administration's repeated calls for a free and open Indo-Pacific have fallen flat in various capitals, which many see as very thin gruel, begging the issue of how the US intends to remain relevant to the regional future," Mr Pollack said.
- Reuters/ RNZ