The letter, reported by The New York Times, says that Israel’s current military campaign in Gaza, in which Israeli forces have killed more than 31,000 Palestinians, is failing to achieve its own stated goals of eliminating the Palestinian group Hamas and freeing the remaining Israeli hostages held in Gaza.

“As donors and activists, we have committed much time and treasure in helping increase the turnout of likely Biden voters, particularly among young voters and voters of color,” the letter states.

“Many of these voters are now questioning whether the Democratic Party shares their values. If they stay home or vote for a third-party candidate, there is the very real danger that President Biden will be defeated in November.”

The letter goes on to say how the election of Donald Trump in November would be “a disaster for our country” and that the signatories “fear that the Gaza war is increasing the chances of that occurring”.

“Because of the disillusionment of a critical portion of the Democratic coalition, the Gaza war is increasing the chances of a Trump victory.”

According to The New York Times, among the letter’s signatories are several individuals who gave six-figure donations to Biden’s presidential campaigns in 2020 and 2024.

A handful have also given more than $1m to Biden’s campaigns, the newspaper reported.

Israel’s war on Gaza began on 7 October, when Hamas led a surprise attack on southern Israel, killing around 1,200 people and taking at least 250 hostages back to the enclave.

In response, Israel declared war, launching a military operation that began with an indiscriminate bombing campaign followed by a ground invasion of Gaza.

So far, Israeli forces have killed more than 31,000 Palestinians, laid siege to and attacked hospitals, targeted other civilian infrastructure, including schools and mosques, and attacked medical workers.

Since the beginning of the war, Biden declared his full-fledged support to Israel, also visiting Israel.

He has also been calling for an additional $14.3bn in military aid to Israel, and has bypassed congressional authority to fast-track weapons to the country.

“Regrettably, President Biden has provided what appears to be unconditional support for the Israeli operation,” the letter states.

“The Biden administration has been providing armaments, including 2,000-pound bombs which have been used to flatten entire civilian neighborhoods, causing massive casualties with a high ratio of women and children.”

The president’s stance comes at odds with many voters in his base, who favour an end to the war. Two-thirds of US voters support a permanent ceasefire in Gaza, according to a poll conducted by Data for Progress.

And a smaller but significant number, 35 percent, believe Israel is committing genocide in Gaza, according to a YouGov poll.

“We are asking the Biden administration immediately to change course,” the letter said.

“Conditions need to be placed and monitored on any further military, financial, or diplomatic aid. All indiscriminate bombing and demolition must stop.”

However, it is unclear whether the letter for Biden would sway the president from changing course on his policy on Gaza.

On Tuesday, the League of Conservation Voters, a leading climate organisation, said it would put $120m towards Biden’s presidential reelection bid, and outside of independent groups, Biden’s campaign says it expects to raise and spend more than $2bn on its campaign.