The U.S. Secretary of State has warned that a move by Israel's parliament towards annexation of the occupied West Bank would threaten Washington's plan to end the conflict in Gaza.

That's not something we can be supportive of right now, Marco Rubio said before leaving for Israel as part of U.S. efforts to shore up a fragile ceasefire deal.

In an apparent attempt to embarrass Israel's Prime Minister Benjamin Netanyahu, far-right politicians took the symbolic step of giving preliminary approval to a bill granting Israel authority to annex the West Bank.

The Palestinians claim the West Bank - occupied by Israel since 1967 - as part of a hoped-for independent state.

Last year, the International Court of Justice - the UN's top court - stated that Israel's occupation was illegal.

Netanyahu has previously supported annexing West Bank land but has avoided advancing this due to the risk of alienating the U.S. - Israel's most important ally - and Arab countries that have established relations with Israel.

Ultra-nationalists in Netanyahu's coalition have repeatedly called for the annexation of the West Bank, though the bill was put forward by MPs outside the government.

The bill passed with a 25-24 vote, although it remains unclear whether it can secure a majority in the 120-seat Knesset.

The Palestinian foreign ministry condemned the Knesset's move, asserting Israel has no sovereignty over Palestinian land.

Israel has constructed approximately 160 settlements housing 700,000 Jews during its occupation of the West Bank and East Jerusalem, where an estimated 3.3 million Palestinians coexist.

As he boarded the plane to Israel, Rubio reiterated that annexation would be counterproductive and threatening for peace, reiterating U.S. opposition to such measures.

This visit follows trips by U.S. Vice-President JD Vance and two special envoys, as the Trump administration pushes for the next steps in a 20-point Gaza peace plan. The first phase, which includes a ceasefire and partial withdrawal of Israeli forces, was enacted earlier this month.

Both Israel and Hamas have accused one another of breaches, yet the ceasefire has held so far. Rubio remains optimistic about preserving it, stating, Every day, there’ll be threats to it, but I actually think we’re ahead of schedule in terms of bringing it together.

The second phase of the peace plan consists of establishing an interim government in Gaza, deploying an international stabilisation force, withdrawing Israeli troops, and the disarmament of Hamas.

The ongoing war in Gaza initiated with a Hamas-led attack on southern Israel on October 7, 2023, resulting in the deaths of approximately 1,200 individuals and 251 hostages. In the aftermath of the conflict, over 68,000 Palestinians have reportedly died, according to the Gaza Health Ministry, whose figures are considered reliable by the UN.