US President-elect Donald Trump said Saturday that the UN vote demanding Israel halt settlements in the Palestinian-claimed West Bank would make a peace deal “much harder,” but not impossible, to attain.

“The big loss yesterday for Israel in the United Nations will make it much harder to negotiate peace.Too bad, but we will get it done anyway!” Trump tweeted.

The UN vote Friday marked a stark turnabout in longstanding US custom at the world body. The Security Council passed the measure after the United States abstained, enabling the adoption of the first UN resolution since 1979 to condemn Israel over its settlement policy.

By deciding not to veto the move, the US took a rare step that deeply angered Israel, which accused President Barack Obama of abandoning its closest Middle East ally in the waning days of his administration. Prime Minister Benjamin Netanyahu rejected the resolution Saturday as a “shameful blow against Israel.”

Trump had already issued a curt warning Friday afternoon that his administration could take an adversarial approach to the international body.

“As to the UN, things will be different after Jan. 20th,” the president-elect tweeted shortly after the Security Council passed the resolution by a vote of 14-0.

Even before US Ambassador to the United Nations Samantha Power formally announced that the US would abstain rather than veto the resolution, Senator Lindsey Graham had already warned that the Senate would consider defunding the international body when it reconvenes in 2017.

Speaker of the House Paul Ryan described the US abstention as “absolutely shameful.”

“Today’s vote is a blow to peace that sets a dangerous precedent for further diplomatic efforts to isolate and demonize Israel,” Ryan said. “Our unified Republican government will work to reverse the damage done by this administration, and rebuild our alliance with Israel.”

An Israeli official Saturday evening said that “Trump, members of Congress and Jewish organizations” had been enlisted to “prevent this move by the Obama administration.”

The US’s failure to veto the resolution was the “last sting of President Obama” that exposed his “true face,” the anonymous official said, charging that “the United States acted behind the back in composing and advancing the resolution against Israel. We knew about it through Arab and international sources.”

Netanyahu, meanwhile, thanked Trump for his promise for support at the international body after he takes office.

In a second barb at Obama since the Security Council resolution passed, the prime minister on Saturday evening expressed thanks “to all of our friends in the United States, Republicans and Democrats alike” for their support, while sharing Trump’s vow that things would change at the United Nations after he takes office next month.