"We have decided to continue our intensive work in the coming weeks toward such an agreement," the 12 ministers said in a joint statement on the proposed Trans-Pacific Partnership (TPP).
"Following additional work by negotiators, we intend to meet again next month," they added after four days of secretive talks denounced by activists as a US attempt to railroad a deal.
The TPP is being negotiated by Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, the United States and Vietnam. They make up 40 per cent of the global economy and other countries may join the pact later.
The ministers had arrived in Singapore from the just-concluded World Trade Organisation talks in the Indonesian island of Bali.
President Barack Obama has hailed the TPP as a centrepiece of renewed US engagement in Asia, saying it contains market-opening commitments that go well beyond those in other free-trade accords.
But the complexity of the issues already caused negotiators to miss the original 2012 deadline set by Obama to reach a deal.
TPP negotiators have been divided over a number of issues, including opening up Japan's auto and farm markets and patent issues - in particular on medicines.
US negotiators, backed by the powerful pharmaceuticals industry, want drug companies to get longer patent protection for a new class of drugs called "biologics" which are developed from living tissue.
Drug firms say this is necessary to allow them to recoup investments and continue research for fresh cures.
But activist groups like humanitarian organisation Medecins Sans Frontieres (Doctors Without Borders) say such patent protection would restrict access to cheaper generic drugs for millions of poor people.