Vanuatu's parliament will sit next Wednesday to vote on a motion of no confidence in the government of Prime Minister Charlot Salwai.
The motion, bearing the signatures of 31 MPs, was ruled in order by the Speaker of parliament ahead of a sitting this afternoon.
The government spent Wednesday manoeuvring to shore up its support, swearing in a new health minister, Jerome Ludvunae, and creating two new undersecretary positions.
It said it was confident of its majority support, with about 30 MPs in the 52-member parliament - but correspondents say some MPs are almost certain to have defected.
Nevertheless, the motion is a setback for the government's promise to try and bring stability to a political system plagued by frequent motions and changes of government.
Mr Salwai's government was created after snap elections in January after half the previous government was jailed for corruption, related to payments offered for support in a previous motion.