Palestinian militant group Hamas has turned down an offer to serve in Prime Minister Ahmed Qurei's government.
Hamas enjoys substantial support among Palestinians
"Forming a unity government at this late time will not be useful," a Hamas spokesman said.
The offer was aimed at drawing Hamas into the Palestinian decision-making process ahead of the Israeli withdrawal from the Gaza Strip.
The group has proposed setting up a special committee to co-ordinate Palestinian moves during the pullout.
From next month Israel is due to pull all its 8,000 settlers from Gaza and the troops that protect them, as part of a disengagement plan.
The Palestinian Authority offer was made by Mr Qurei a few days ago.
But the prime minister gave no details of how Hamas might be integrated into a government of national unity.
Hamas spokesman Mushir al-Masri said on Monday that the group had decided to reject the invitation after a series of internal consultations.
The group does not want to involve itself in all the business of government at this stage, says the BBC's Alan Johnston in Gaza.
If Hamas had accepted the offer, it may well have made the Palestinian Authority's relations with Israel very much more difficult, our correspondent says.
Israel views Hamas as being among the worst of its terrorist enemies, a group sworn to Israel's eventual destruction, he adds.
But many Palestinians regard Hamas as having been in the vanguard of the resistance to decades of Israeli occupation.