Danny Russel, the top US diplomat on East Asia, said he made the suggestion as "food for thought" and not as a formal proposal as he met regional counterparts in Myanmar to prepare for a regional summit later this year.
"The claimant states themselves could identify the kind of behavior that they each find provocative when others do it, and offer to put a voluntary freeze on those sorts of actions on the condition that all the other claimants would agree to do so similarly," Russel, an assistant secretary of state, told reporters on a conference call.
"So for example, would they be willing to make a pledge as simple as not to occupy any of the land features in the South China Sea that are currently unoccupied?"
The United States has pushed for years for a code of conduct to lay out rules to prevent the escalation of incidents in the South China Sea, an economically vital waterway in which China has overlapping claims with several other nations.
But Russel acknowledged that tensions have been "going up quickly" in the sea. Riots erupted in Vietnam last month in anger against China's deployment of an oil rig in contested waters.
The Philippines, a US ally, has also seen increasingly tense tussles with China over control of islets and reefs in the sea.
Russel said that the Chinese delegation at the talks in Myanmar offered a "spirited and vigorous defense" of its position, but voiced hope that Beijing understood that other nations' statements were "offered not in the spirit of condemnation, but in the spirit of compromise."
President Barack Obama is expected to travel to Myanmar in November for the East Asia Summit on his second visit to the country formerly known as Burma, a onetime Western pariah which has embraced democratic reforms.
Secretary of State John Kerry is likely to visit Myanmar in August in preparatory meetings for the meetings, which also include a summit of the ASEAN bloc of Southeast Asian nations.