Vanuatu's prime minister has reshuffled his cabinet just four days after a motion-of-no-confidence against his leadership was submitted to parliament.

RNZ Pacific's correspondent in Vanuatu, Hilaire Bule, reports Ishmael Kalsakau has appointed two new ministers whose names were among the 29 signatories to the motion filed by the opposition last Thursday.

They are Samson Samsen who has been given the trade portfolio previously held by Matai Seremaiah, and Christophe Emmelee who is the new Minister for Education replacing Bruno Leingkon.

Bule said two other MPs, whose names also appeared on the no-confidence-motion, Samuel Kalpoelep and Jack Wona, are also reportedly now siding with the government.

Providing these four MPs maintain their loyalty to Kalsakau and no more government MPs defect to the opposition, the prime minister should be able to defeat the motion which can be tabled within seven days of being filed.

There are 52 seats in parliament but one is currently vacant meaning only 26 votes are need to make up the simple majority to carry or defeat the motion.

Parliament is not due to sit until August 16 but the opposition have called for a special sitting this week to hear the leadership challenge.