Washington DC - Vice President Kamala Harris on Thursday condemned the "despicable" and "unpatriotic" burning of an American flag by protesters who rallied in Washington during Israeli Prime Minister Benjamin Netanyahu's address to Congress.

"I condemn the burning of the American flag. That flag is a symbol of our highest ideals as a nation and represents the promise of America. It should never be desecrated in that way," the Democratic presidential candidate said in an unusually strong statement.

She said Wednesday's demonstration featured "despicable acts by unpatriotic protestors and dangerous hate-fueled rhetoric."

The statement, echoed by other senior Democrats, came amid attempts by Republicans to paint the party as pro-Hamas.

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"Anti-American and pro-Hamas rioters burned the American flag in front of the US Capitol, and the woman who wants to be our president is still refusing to condemn it," Senator JD Vance, who is running for vice president alongside Donald Trump, wrote on X just before Harris's statement was issued.

Thousands of demonstrators angry over Israel's assault in Gaza – and the continued weapons shipments from the US that have enabled it – marched on the heavily guarded Capitol on Wednesday as Netanyahu delivered an uncompromising speech to lawmakers.

A group of protesters gathered outside a train station near the Capitol, where they spray-painted monuments, burned Netanyahu in effigy, and lit American flags on fire – a raucous end to a mostly peaceful march.

Harris, who launched her presidential campaign immediately after President Joe Biden announced a shock exit from his reelection bid on Sunday, was set to meet Netanyahu later Thursday. The Israeli leader will meet separately with Biden.

The White House has struggled to thread the political needle in maintaining traditional support for Israel amid its brutal assault on Gaza, which has been heavily condemned by human rights groups and left-leaning voters in the US.