Ehud Olmert, the Israeli prime minister, on Sunday called on the international community to join Israel in shunning the new government, saying: "The platform of the new government includes very problematic elements."
He told the Israeli cabinet that he will not work with the new body, but would maintain contact with Mahmoud Abbas, the Palestinian president and leader of Fatah.
Norway announced on Saturday that it would now recognise the incoming government.
"This is just a ploy to regain international hand-outs with smoke and mirrors"
LeotheIsaurian, Detroit, US
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Jonas Gahr Stoere, the Norwegian foreign minister, said he was satisfied the unity government had taken sufficient steps towards meeting international demands.
Russia and France have also indicated a willingness to work with the Fatah-Hamas coalition.
Arab countries including Syria, Jordan, Qatar and Yemen have called for the aid boycott to end.
However, Israel has called on the Quartet group - the US, EU, UN and Russia - to maintain its sanctions, which were imposed on the Palestinian Authority one year ago after the election of a Hamas government.
The US said it was "disturbed" by the Haniya's reiteration of the Palestinian right to resist Israeli occupation during his speech before the parliamentary vote on the government.
"The national unity government's platform reference to the right of resistance is disturbing and contradicts the Quartet principles of renunciation of violence," Nancy Beck, a US state department spokeswoman, said.
Israeli officials have said that they are worried that European nations will follow Norway's lead and end their aid suspension.
Ziyad Abu Amr, the new foreign minister, said: "The Israeli government is weak and is running away from negotiations by clinging to old irrational positions."
Ministers in the West Bank will have to take part in the new administration's first cabinet meeting on Sunday by video link because of Israeli restrictions on travel between the Palestinian territories.
The new government was given an overwhelming endorsement by the Palestinian parliament, who approved it by 83 votes to 3.
The incoming cabinet was later sworn in by Abbas.
Haniya said: "Today is the beginning of a new era.
"Today's events are a source of pride for the Palestinians and the Arab nation."
On the streets of Gaza City, the unity government was welcomed.
Sadi Shurab, 36, said: "We hope this government ... ends the chaos and the economic boycott.
"We hope it returns salaries to the government employees and provides work for the unemployed."
Abd al Wahab Salim said: "I am happy with the announcement of the unity government, but I don't feel like partying ... I want a life of dignity without fear."