Speaking on the sidelines of an ASEAN regional meeting in Pattaya, Thailand, Vietnamese Deputy Foreign Minister Pham Quang Vinh said ASEAN had been pushing for talks to begin.
"ASEAN thinks it is time to start talks to achieve a code of conduct as soon possible," he said.
But he says the grouping is meeting stoic resistance from China.
The nation has rejected proposals for a multilateral code of conduct for the South China Sea, preferring to try to negotiate disputes with each of the far less powerful individual claimants.
A Thai foreign ministry official, Sihasak Phuangketkeow, says it might take another two years to agree a formal code of conduct.
Carl Thayer of Australia's University of New South Wales said China was unlikely to make any decision on the code of conduct until its once-a-decade leadership change is fully complete next year.
"I suspect because of changes in personnel likely to occur nobody in China is willing to commit themselves to something of this magnitude," he said.
"There can be no compromise at the moment, coming from China.
"Leaders would be seen to be weak."
China has stepped up activity in the region, including establishing a military garrison on one of the disputed islands.
The stakes have risen in the area as well as the US military shifts its attention and resources back to Asia, emboldening its long-time ally the Philippines and former foe Vietnam to take a tougher stance against Beijing.