The Vanuatu government of Edward Natapei is to face a no-confidence motion when parliament resumes tomorrow.
The leader of the opposition, Serge Vohor, sent a letter to Mr Natapei yesterday asking him to resign.
Rumours have been rife that the government was about to be toppled, but the prime minister says he sought and received an assurance by his coalition partners they would support him.
But political analysts say the opposition now has the numbers to carry the no-confidence motion.
Our correspondent says one issue weighing on the ruling coalition is the seeming inability of the government to remove from the board of the Maritime Authority, the previous director who, it's been alleged, misappropriated funds.