"It's been an excellent basis, an excellent platform for working together," said Negroponte, the number two US diplomat after Rice, after talks with ministers from the Association of Southeast Asian Nations (Asean).

"It's been an opportunity to emphasise the great importance that the United States attaches to our relationships within Asean," he said.

It is the second time in three years that Rice has skipped Asia's main security meeting, the Asean Regional Forum, but officials said they understood she was in the Middle East and welcomed the US role around the world.

"These are challenging times that we live in, and US leadership is critical," Singapore Foreign Minister George Yeo said in a speech on behalf of Asean to welcome Negroponte.

"US investment and markets have helped lay the foundations for the rapid growth for the region's economies," he said. "However, the US stays engaged, this can be a new golden age for Asia and the world."

Asean is looking to create a single market by 2015, five years earlier than the original target date -- which Negroponte said was a signal for expanded cooperation with the United States in future.

"We think this will represent great, great opportunities in our relationships with the Asean countries," he said. "We have had a very good day of business."

Thursday's annual ARF security summit features dozens of side meetings. Negroponte and the top US negotiator on North Korea, Christopher Hill, met Chinese Foreign Minister Yang Jiechi and other regional officials.