United Nations Secretary-General Antonio Guterres on Wednesday called on Israel to scrap plans to annex parts of the occupied West Bank, a move that could occur as early as next week.

"We are at a watershed moment," the UN chief told a virtual meeting of the Security Council.

"If implemented, annexation would constitute a most serious violation of international law, grievously harm the prospect of a two-state solution, and undercut the possibilities of a renewal of negotiations. I call on the Israeli Government to abandon its annexation plans," he said.

Israeli Prime Minister Benjamin Netanyahu made annexation a major pledge during campaigning, ahead of the latest round of national elections held in March.

The proposal would see sovereignty extended to roughly 30 percent of the West Bank, covering most of the Jordan Valley.

In response, Palestinian leaders have cut ties with Israel and the United States, which backs the plan.

The UN envoy for the Middle East, Nikolay Mladenov, warned the council that three decades of international peace efforts could be at stake.

"Recognizing that both peoples have a right to live in their ancestral home, 27 years ago, Israeli and Palestinian leaders agreed to embark on a noble but difficult road, to resolve the conflict through negotiations, without taking unilateral action, and in order to reach a final status agreement on a just peace," he said, speaking from Jerusalem. "Today we are further than ever from this goal."

In supporting the secretary-general's appeal to Israel, Mladenov feared annexation could trigger instability across the occupied Palestinian territory and even beyond.

He urged the international community to work to get the parties to step back and continue the dialogue toward peace.

Zhang Jun, China's UN ambassador, read a statement at the meeting on behalf of Wang Yi, Chinese state councilor and foreign minister.

"The Middle East is again at a crossroad between peace and turbulence. Shouldering the primary responsibility for the maintaining of international peace and security, the Security Council should and must play its role," Zhang said.

Zhang reiterated China's position, stressing that international consensus must not be contravened. "The two-state solution is a bottom line of international justice."

"China supports the establishment of an independent state of Palestine that enjoys full sovereignty on the basis of 1967 borders and with East Jerusalem as its capital. Israel's right to survival and legitimate security concerns should be fully respected," he said.

Xinhua contributed to this story.