Washington DC Mayor Muriel Bowser announced on Tuesday she will not seek re-election next year for a fourth term.

Bowser, who has been mayor since 2015, says she was looking to the future and that her administration had "laid the groundwork for others to build upon".

The Democratic mayor oversaw the US capital city through several periods of turmoil over the last decade, most recently clashing with US President Donald Trump over his deployment of National Guard troops across the city as well as the mass lay-offs of federal workers.

Her decision is likely to open up a crowded field of candidates seeking to replace her in the Democratic stronghold.

"It has been the honour of my life to be your mayor," Bowser said in a video announcement. "But today, with a grateful heart, I am announcing that I will not seek a fourth term... For the next 12 months, let's run through the tape and keep winning for DC."

She listed what she said were accomplishments after 10 years in office, including increasing housing, steering the city through the COVID pandemic, and bringing major infrastructure investments to low-income areas of the federal district.

During Trump's first term, the president clashed with Bowser over several issues including crime and the city's response to racial reckoning protests in 2020. She approved a Black Lives Matter mural on the major thoroughfare leading up to the White House, a move that angered the president.

In the days after the 6 January Capitol riot, Trump accused Bowser and US House Speaker Nancy Pelosi of refusing an offer to send in the National Guard troops. Bowser refutes the claim and said Trump never extended the offer.

But in recent months, she has faced criticism for not doing more to resist the Trump administration's surge of federal agents and soldiers onto the streets.

She has thanked Trump for offering agents to help local police deal with crime but expressed dissatisfaction with the presence of uniformed soldiers on the streets.

Last week, a federal judge ruled Trump's deployment of National Guard troops was illegal.

City officials also removed the Black Lives Matter mural after Republicans in the US Congress threatened to withhold federal funding for roads in the city.

The District of Columbia is not a US state and depends on the federal government for large portion of its budget. Its laws are subject to a veto by US Congress and the president. Republicans currently control both chambers of Congress and the White House.

Bowser, like many mayors before, has campaigned for the district to become the 51st state of the country, a move that would grant local officials and residents greater say in how the territory is run.

At least four candidates have notified the district's elections board about their intention to run in next November's mayoral elections. Local media reported two city council members are also expected to join the field.