The U.S. Secretary of State has said 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 - said Israel's occupation was illegal.

Netanyahu has previously spoken in support of annexing West Bank land but has not advanced this due to the risk of alienating the U.S. - Israel's most important ally - and Arab countries which have built relations with Israel after decades of enmity.

Ultra-nationalists within Netanyahu's governing coalition have repeatedly called for Israel to annex the West Bank outright, though the bill was put forward by MPs outside the government.

The bill passed in a narrow 25-24 vote, and it remains uncertain if it has the support to win a majority in the 120-seat Knesset (parliament); Netanyahu has avenues available to delay or defeat the bill.

The Palestinian foreign ministry condemned the Knesset's move, stating that Israel would have no sovereignty over Palestinian land.

According to international law, the settlements Israel has built, housing approximately 700,000 Jews during its occupation of the West Bank and East Jerusalem, are classified as illegal. An estimated 3.3 million Palestinians live alongside these settlements.

As he boarded the plane to Israel, Rubio reiterated that annexation would be counterproductive and threatening to the peace deal, highlighting U.S. opposition to annexation.

His visit comes shortly after trips by U.S. Vice-President JD Vance and two special envoys as the Trump administration is striving to initiate talks on the second critical phase of the 20-point Gaza peace plan.

The first phase, which includes a ceasefire alongside a partial withdrawal of Israeli forces and increased aid, commenced earlier this month.

The war in Gaza erupted following a Hamas-led attack on southern Israel on October 7, 2023, which resulted in about 1,200 fatalities and 251 hostages taken. Since then, over 68,000 Palestinians have reportedly lost their lives due to the conflict.