WASHINGTON, March 28 (Reuters) - The United States is willing to make agricultural concessions to reach a new world trade deal if other countries open their markets to more U.S. exports, President George W. Bush said on Friday.

"We're willing to make serious concessions on the agricultural front, but we expect other nations to open up their markets on manufacturing as well as services," Bush said at a news conference after meeting Australian Prime Minister Kevin Rudd.

Bush said the Doha round, which is now in its seventh year, was a major topic of his conversation with Rudd.

"I said it's possible to achieve a Doha round. He, too, believes we should work to achieve a Doha round," Bush said.

On Monday, Brazil's chief Doha negotiator Robert Azevedo said negotiators were closer than ever to an agreement, but there still was no certainty of success.

The United States and the European Union both face demands to make deep cuts in their agricultural subsidies and tariffs, but want major developing countries such as India and Brazil to open their markets in exchange.

Negotiators have been working in Geneva toward a possible ministerial-level meeting in April or May, where it is hoped a long-awaited breakthrough would occur.

"If ever the global economy needs a psychological injection of some confidence in the arm, it's now, and that can be delivered by a positive outcome on Doha," Rudd said.

A successful agreement can only be achieved if all the major players -- including Brazil, India, the United States, the European Union and the Cairns Group of agricultural exporters led by Australia -- do their part, Rudd said.

"It takes more than two to tango. It takes a lot of people to tango when it comes to the Doha round," Rudd said.

The leaders said the United States and Australia would work together to try to bring the Doha round to a successful close.

The longtime allies also are building on the three-year- old U.S.-Australia free trade agreement by signing an "open skies" agreement on Monday to liberalize air travel between the two countries, Bush said.