Palestinian Prime Minister Ismail Haniya said on Sunday the participation of his Hamas group in a unity government hinged on winning guarantees Western economic sanctions would end once a new administration was in place.
"We need documentation and we need a greater assurance. We need to feel that they will be committed to lifting the siege in return for this big step," Haniya told reporters.
Palestinians hope a unity government, which Hamas and President Mahmoud Abbas's Fatah faction have been trying to form, can lead to a resumption of financial aid suspended by Western nations after the group came to power in March.
Hamas says it has a legitimate right to fight occupation, has rejected Western demands to renounce violence, recognise the Jewish state and accept existing interim peace deals.
"We are not going only for a photo opportunity. We want to lay the basis for real national unity, for a real political partnership," Haniya said.
"Therefore, the United States, the Europeans and our brothers the Arabs must shoulder their full responsibility to end the siege of the Palestinian people," he said, repeating a demand for Israel to free Palestinian prisoners and jailed Hamas legislators.
The aid boycott has deepened the economic crisis in the occupied West Bank and in the Gaza Strip. About 165,000 government employees in the Palestinian territories have not received full wages for eight months.
Haniya said Hamas and Fatah were engaged in "deep and continuing dialogue" and that more time was needed before a unity government of technocrats could be finalised.
He expressed disappointment that a promise a week ago by Arab foreign ministers to break a Western ban on bank transfers to the Palestinian Authority had not been implemented.
At their meeting in Cairo, the ministers gave no details of how they would help banks avoid US sanctions to send between $100 million and $150 million in outstanding Arab aid pledges to the Palestinians.
"We appreciated the decision and we regarded it as a distinctive step to end the siege, but it was not translated on ground," Haniya said. "The Arabs backtracked in the face of American might."