The deal is "a milestone" says Australia.
South East Asian economy ministers have signed a free trade deal with Australia and New Zealand.
Members of the 10-member Association of South East Asian Nations (Asean) struck the deal on the first day of a summit in Thailand dominated by the downturn.
It is thought the deal could bolster the combined economies of the nations by up to $48bn (£33.8bn) by 2020, but will do little to ease current woes.
Asean members include Indonesia, Singapore, Malaysia and Philippines.
Talks on establishing the 12-nation free trade zone began in 2004.
The new agreement means the South East Asian bloc has forged free trade links with all its key neighbour economies. It earlier signed deals with China, Japan and South Korea.
Asean also has plans to establish a single market and manufacturing base by 2015, in a bid to remain competitive with the likes of India and China.
Australian Trade Minister Simon Crean said the agreement was "a milestone" in his country's economic engagement with the region.
And New Zealand's Trade Minister Tim Groser said it was both a "very big deal commercially" and "a significant deal politically".
"We viewed South East Asia as a source of threat, instability and danger. To move from that to signing an agreement that sees Southeast Asia as a source of tremendous economic opportunity is a remarkable change over a 30-year period," he added.
The meeting in the Thai resort of Cha-Am is also set to witness two Asean accords on goods trade and investment.
The other Asean members are Thailand itself, Brunei, Cambodia, Laos, Myanmar, and Vietnam.
Now in its 14th year, the annual summit traditionally focused on human rights, but the worldwide financial crisis is set to be top of the agenda this year.
Several powerful Asian economies have seen their fortunes reversed as the economic downturn continues to bite.
Singapore, the region's most advanced economy, is already in a recession, while Thailand's economy shrank in the fourth quarter. Other economies, such as Malaysia and the Philippines, are suffering weak demand for their exports.
The global financial turmoil has raised fears about protectionism to protect home-grown industry. Any such moves could particularly affect South East Asian economies, as several derive a large share of their income from exports.