Washington has warned it could withhold funds from the already cash-strapped Palestinian Authority and Israel has stopped tax transfers.
Palestinian president Mahmud Abbas has returned home to a hero's welcome after winning upgraded UN status.
"Now we have a state," Abbas told cheering crowds at his headquarters in the Israeli-occupied West Bank."
"Palestine has accomplished a historic achievement at the UN," he added, three days after the United Nations General Assembly granted the Palestinians non-member state observer status in a 138-9 vote.
"The world said in a loud voice ... yes to the state of Palestine, yes to Palestine's freedom, yes to Palestine's independence, no to aggression, no to settlements, no to occupation," Abbas told the ecstatic audience.
But the Palestinian UN success has not been without repercussions.
Washington has warned it could withhold funds from the already cash-strapped Palestinian Authority and Israel said on Sunday it would not transfer millions of dollars in tax duties it levies from the Palestinians.
On Friday, Israel revealed plans to build 3000 settler homes in the West Bank, including annexed east Jerusalem, and to revive a dormant project in a highly contentious area known as E1, a corridor that runs east from the far edge of the holy city into the heart of the West Bank.
UN leader Ban Ki-moon warned on Sunday that any Israeli move to revive that project would deal an "almost fatal blow" to any prospects for peace.
"Settlements are illegal under international law and, should the E1 settlement be constructed, it would represent an almost fatal blow to remaining chances of securing a two-state solution," Ban's office said in a statement.
In Ramallah, Abbas pledged that after the victory at the United Nations, his "first and most important" task would be working to achieve Palestinian unity and reconciliation between his Fatah faction and the Hamas rulers of Gaza.
"We will study over the course of the coming days the steps necessary to achieve reconciliation," he said, as the crowd chanted: "The people want the end of the division."
In Gaza, Hamas official Salah Bardawil said the Islamist group was calling "for urgent meetings to achieve reconciliation".
The return was a moment of triumph for Abbas, who last year tried and failed to win the Palestinians full state membership at the United Nations.
That bid stalled in the Security Council, where the veto-wielding United States has vehemently opposed it.
The new UN upgrade gives the Palestinians access to a range of international institutions, including potentially the International Criminal Court, and raises their international profile after years of stalled peace talks with Israel.
Abbas was received with a full honour guard, walking along a red carpet at the Ramallah presidential headquarters known as the Muqataa, where he shook hands with waiting dignitaries.
He laid a wreath and said a brief prayer at the grave of Palestinian leader Yasser Arafat, who is buried inside the presidential complex. He later dedicated the UN victory to the former president's memory.
"Our people everywhere, raise your heads up high because you are Palestinians," he said. "You are stronger than the occupation ... because you are Palestinians.
Abbas's return drew supporters from across the West Bank.