Some U.S. officials had been advocating a shift in Washington's position that would allow limited diplomatic contacts with cabinet ministers from moderate President Mahmoud Abbas's Fatah faction and other parties.
But a senior Palestinian official said: "The Americans have informed us that they will be boycotting the new government headed by Hamas. The Fatah and independent ministers will be treated the same way that Hamas ministers are treated."
Diplomats familiar with discussions on the issue confirmed Washington's intention to shun members of the unity government unless it satisfied international calls for Hamas to recognize Israel, renounce violence and accept interim peace accords.
U.S. contacts with Abbas would not be affected although diplomatic sources said relations have been strained by his power-sharing deal with Hamas Islamists, a pact that fell short of meeting the demands for the policy changes.
U.S. officials declined to comment and said Washington was waiting to see how a new government would shape up.
Talks on 3-way summit falter over final status issue
A meeting held earlier this week between Israelis and Palestinians to prepare for an upcoming trilateral summit faltered over whether the agenda should include discussions on a final status agreement.
The meeting between Prime Minister Ehud Olmert, Abbas and U.S. Secretary of State Condoleezza Rice is set to take place in Jerusalem on Monday.
Olmert's bureau chief Yoram Turbowicz and his political advisor Shalom Turjeman met Monday with chief Palestinian negotiator Saeb Erekat and Abbas' chief of staff, Rafik al-Husseini, but were unable to resolve their differences.
The Palestinian representatives at the meeting reiterated their demand that the summit address permanent settlement issues, but the Israeli representatives rejected the topic as out of hand.
Rice is scheduled to meet with Abbas in Ramallah on Monday to try to reach an agreement on the agenda for the summit.
Abbas held a phone conversation Wednesday with a top U.S. government official who said that the U.S. would cooperate with the unity government only if the government accepts the conditions set forth by the Quartet of Middle East peace mediators: recognizing Israel, abiding by prior agreements and renouncing violence.
The official reiterated prior statements conveyed to Erekat and PLO working committee member Yasser Abed Rabbo during their recent visit to Washington, the Abbas must bring about a change in Hamas' attitude. Palestinian Prime Minister Ismail Haniyeh has already announced that the new government will not recognize Israel.
During their meeting in Amman earlier this week, Russian President Vladimir Putin also told Abbas that despite Russian statements supporting the Mecca agreement over a unity government, Moscow would only cooperate with the new government if it accepts the Quartet's demands.