Britain and Portugal were on Sunday expected to recognise a Palestinian state, ahead of a key week at the United Nations gathering where a suite of nations are set to do the same to pressure Israel over Gaza.

A growing number of long-time Israeli allies have shifted positions in recent months as Israel has intensified its Gaza offensive.

The besieged Palestinian territory has suffered vast destruction, death and lack of food that have resulted in a major humanitarian crisis.

World leaders will gather for a key debate at the UN General Assembly in New York this coming week where the so-called two-state solution to the Israeli-Palestinian conflict will be front and centre.

Around 10 nations are expected to recognise a Palestinian state in the coming days, with UK media reporting that Prime Minister Keir Starmer would announce the policy shift on Sunday – over fierce Israeli objection.

Starmer had said in July that Britain would formally recognise the State of Palestine if Israel did not take "substantive steps" towards a ceasefire with Hamas by the time the UN General Assembly convened.

The Labour leader said at the time that the move would make "a contribution to a proper peace process, at the moment of maximum impact for the two-state solution".

In response, Israeli Prime Minister Benjamin Netanyahu accused him of rewarding "monstrous terrorism" and appeasing "jihadist" ideology.

Portugal's foreign ministry said on Friday that it would also formally declare its recognition on Sunday.

Lisbon had already announced in July that it intended to do so, citing the "extremely worrying evolution of the conflict" as well as the humanitarian crisis and Israel's repeated threats to annex Palestinian land.

France and Canada are among the other Western nations planning to recognise a Palestinian state at the UN gathering in the coming week.

Israel has vehemently opposed the moves and has reportedly threatened to annex the West Bank in response. (AFP)