Palestinian leader Mahmoud Abbas has postponed a national speech amid concern there could be a new snag to a power-sharing deal sealed last week.
Fatah and Hamas reached agreement in Mecca last week
Mr Abbas's Fatah faction and Hamas, of Prime Minister Ismail Haniya, had agreed to form a new government of national unity.
But the two sides have been unable to agree on a number of key appointments.
Factional fighting between Hamas and Fatah claimed more than 90 Palestinian lives between December and this month.
Mr Abbas had planned to address the Palestinian people on Thursday ahead of a meeting with Mr Haniya in Gaza. The meeting is still scheduled to go ahead.
Officials said Hamas had presented new conditions before it would resign the government that it leads - an essential step for the power-sharing deal to start.
Hamas, which has governed on its own during the past year, is unhappy about moves to dissolve a security force that it has established.
There are also disputes over appointments to key cabinet posts.
One official told Reuters the conditions related to "the interior minister and the foreign minister and the executive force (the Hamas security force)".
The official said: "Hamas has made several unacceptable conditions which cannot be implemented."
Other Hamas concerns were said to include the civil service. It wants Mr Abbas to appoints dozens of Hamas loyalists to top posts.
The power-sharing deal was agreed last week in Mecca, Saudi Arabia, although some details on the cabinet were left undecided. Hamas agreed to respect past Palestinian agreements that recognise Israel.
The EU, US and Russia have maintained a crippling economic boycott of the Palestinian government since Hamas won legislative elections in January 2006.