SINGAPORE - Prime Minister John Key is predicting "billions and billions" in additional export returns down the track after US President Barack Obama today said he would work with New Zealand and other free trading nations to slash tariff barriers in the Asia-Pacific region.

Speaking in Japan prior to flying to Singapore for the Apec leaders' summit which got under way in his absence, the president singled out the existing Trans Pacific Partnership trade agreement between New Zealand, Singapore, Chile and Brunei as the potential mechanism for building a huge free trade area spanning the Pacific.

While offering no timetable for the ambitious plan, Mr Obama said the United States would restart talks he earlier put on hold about potentially joining "Transpac".

"The United States will ... be engaging with the Trans Pacific Partnership countries with the goal of shaping a regional agreement that will have broad-based membership and the high standards worthy of a 21st century trade agreement."

That signal was just what New Zealand ministers and officials had been hoping for, but did not necessarily expect from a president facing domestic presure to put a freeze on negotiating more free trade deals.

Mr Key said the president's statement was "very good news".

"It shows the Americans are committed to free trade... It shows we have the right strategy (in) focusing on the Asia-Pacific region.

"The bus is leaving the station. The Americans are on board. And so are the Kiwis."

US Trade Representative Ron Kirk said the goal of joining the TransPac would be achieved in close consultation with the US Congress, which is holding up the ratification of a free trade agreement with South Korea.

"We seek with current and future TPP participants to shape a platform with the scope and coverage and high standards to successfully integrate the Asia-Pacific economies," Mr Kirk said.

The previous Bush administration began negotiations last year with Transpac. But following his election to the White House, Mr Obama put those talks on hold pending a review of United States trade policy.

He has since come under criticism for letting America's trade policy rest in limbo while Asian economies steal a march by negotiating free trade arrangements with one another.