Crowds are gathering for a demonstration that organisers say will show solidarity with Israel in its war with Hamas and condemn rising antisemitism.
Several thousand people, many draped in Israeli and American flags, have gathered round the National Mall as streets were closed around much of downtown amid heightened security.
Protests have taken place across the world in response to Hamas's deadly attack on Israel on 7 October, in which more than 1,000 people died.
Israel has vowed to wipe out the militant group, subjecting Palestine to near-constant aerial bombardment and a blockade which has led to a severe shortage of fuel, water, food and medical supplies.
According to advocacy groups, the conflict has sparked a rise in antisemitic and Islamophobic incidents - including violent assaults and online harassment - in the US.