The United States will "unquestionably veto" a UN draft resolution calling for the protection of Palestinians in Gaza and the West Bank, US Ambassador Nikki Haley said on the eve of a Security Council vote on Friday.
Haley described the text put forward by Kuwait on behalf of Arab countries as a "grossly one-sided approach that is morally bankrupt and would only serve to undermine ongoing efforts toward peace between the Israelis and Palestinians."
The vote is scheduled for 3:00 pm (1900 GMT) on Friday.
The United States circulated its own rival draft resolution blaming Hamas for the recent flare-up in Gaza and demanding that Hamas and Islamic Jihad "cease all violent activity and provocative actions, including along the boundary fence", according to the text seen by AFP.
It was unclear whether there would be a vote on the US text, which could fail to garner enough support.
Kuwait presented its draft two weeks ago, initially calling for an international protection mission for the Palestinians as protests turned violent on the Israeli-Gaza border.
At least 122 Palestinians have been killed by Israeli fire in the unrest since the end of March.
A final, watered-down version however urges "the consideration of measures to guarantee the safety and protection" of Palestinian civilians and requests a report from Secretary-General Antonio Guterres on a possible "international protection mechanism."
"The United States will unquestionably veto Kuwait?s draft resolution," Haley said in a statement.
It would be the second time that Haley has resorted to US veto power to block a UN measure on the Israeli-Palestinian conflict.
In December, Haley vetoed a measure that rejected President Donald Trump's decision to move the US embassy to Jerusalem after all 14 other council members supported it.
- Deadlock at the UN -
The council has been deadlocked for weeks over how to respond to the violence in the Gaza Strip -- even as a UN envoy warned this week that the crisis could escalate into all-out war.
"The resolution calls on Israel to immediately cease its actions in self-defense, but makes no mention of Hamas' aggressive actions against Israeli security forces and civilians," Haley said in a statement.
She also delivered a blunt warning to European countries and other council members that choosing to "vote in favor of this resolution will clarify their own lack of fitness to take part in any credible negotiations between the two parties."
The UN envoy for the Middle East, Nickolay Mladenov, this week warned the Security Council that Gaza was "close to the brink of war" following a serious escalation between Israel and Palestinian militants in the Hamas-ruled enclave.
An exchange of fire on Tuesday and into the early hours of Wednesday began with a barrage of rocket and mortars into Israel from Gaza, prompting Israel to respond with strikes on 65 militant sites in the Gaza Strip.
It was the worst flare-up since the 2014 war in Gaza.
Diplomats have said the Palestinians may turn to the UN General Assembly to win support for the measure if the vote fails at the Security Council as expected.
A draft resolution requires nine votes to be adopted in the 15-member council and no veto from the five permanent members -- Britain, China, France, Russia and the United States.
Palestinian relatives of Mohammed al-Radeia -- one of at least 122 Palestinians killed by Israeli fire since the end of March -- mourn during his funeral in the northern Gaza Strip on May 28, 2018