A source with knowledge of the trip said that the "diaries" of Sir Keir Starmer and Benjamin Netanyahu did not align.

In addition, a planned meeting between the prime minister and Ron Dermer, Israel's minister of strategic affairs, was cancelled because the senior Israeli official had delayed his travel to the United Nations General Assembly by a day.

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The absence of talks between the British and Israeli leaders came despite Israel significantly expanding an offensive against Hezbollah in Lebanon, prompting calls by the UK and other allies for an immediate ceasefire amid fears of escalation into a regional war.

It also followed condemnation by Mr Netanyahu of a decision by the UK government to suspend some arms export licences to Israel, describing it earlier this month as a shameful move that would embolden Hamas - another Iran-backed militant group that the Israeli military is fighting.

The source said that a meeting between Sir Keir and Mr Netanyahu in New York had not been pre-planned - but there had been hopes it might happen.

"I think there were definitely attempts [to arrange talks] but the diaries just did not work," the source said, speaking on the condition of anonymity.

"We were hopeful for a meeting" but one was not agreed.

The Jewish Chronicle newspaper also reported that the two leaders did not meet, despite both being in New York at the same time.

It quoted Downing Street sources as insisting this was not a snub and that the government is "in touch with the Israelis all the time".

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By contrast, the British prime minister did hold talks with his Lebanese counterpart.

Sir Keir gave Najib Mikati his "sincere condolences… for the loss of civilian life in recent weeks", Downing Street said in a statement.

"They discussed the escalating conflict in Lebanon, and agreed on the importance of an immediate ceasefire and a negotiated solution."

The British leader used his maiden address at the UN General Assembly to call for Israel and Hezbollah - which is backed by Iran and whose military wing is considered by the UK to be a terrorist organisation - to agree to a ceasefire, saying "escalation serves no one".

Sir Keir implored the two sides to "step back from the brink".