A Marshall Islands negotiator says US demands to change immigration provisions could derail the signing of a new agreement that governs the two countries' relationship.
Robert Muller says the new so-called Compact of Free Association has to be submitted to the US Congress for consideration and approval urgently because the current one lapses in six months.
The Marshall Islands wants to keep visa-free access for its workers and students but the US seeks to tighten the rules in part over the illegal adoption of Marshall Islands babies.
The immigration question is a non-expiring provision of the Compact, with Mr Muller saying it can be resolved in separate government-to-government talks.
Under the Compact, the Marshall Islands gets more than half of its national budget.
The Marshall Islands has been used for US nuclear weapons tests and now houses a key base for the US missile defence system.