London (AFP) - US House Speaker Nancy Pelosi said Monday her Democratic Party must avoid the "menace" of liberal policies pushed by rising political stars if it wants to beat President Donald Trump in the 2020 election.

The top congressional Democrat used an appearance at the London School of Economics to set out a centrist vision that could help woo Republican voters frustrated with Trump's approach.

She followed standard US diplomatic protocol of senior officials not criticising the president while abroad.

But she made explicitly clear that new Congresswoman Alexandria Ocasio-Cortez -- an emerging force in US politics who is often simply referred to as AOC -- and fellow young progressives elected in 2018 represented only the margins of American society.

"When we won this election, it wasn't in districts like mine or Alexandria's," Pelosi said in reference to the November midterms in which the Democrats gained control of the House of Representatives.

"Those are districts that are solidly Democratic -- this glass of whatever would win with a D next to its name in those districts," said the Speaker after picking up a glass off a coffee table.

Pelosi touted her own liberal upbringing and accomplishments representing the deeply Democratic voters of San Francisco.

"I can compare my liberal credentials across the board. I said to them: 'Anything you're about, I got that sign in my basement 20 years ago'," Pelosi said.

But "what we are saying is, to have a message that appeals to people in a way that does not menace them," she said.

"I share those values -- but we must win."

- Anti-Semitism rows -

Pelosi is officially in London to gauge progress in Britain's stalled efforts to withdraw from the European Union after 46 years.

But her stay has coincided with an ugly war of words that has pitted Trump against the new breed of Democrats like Ocasio-Cortez and Ilhan Omar.

Trump accused Omar -- the first black Muslim woman elected to Congress -- in a tweet Monday of making "anti-Semitic, anti-Israel and ungrateful U.S. HATE statements".

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Their latest spat concerns Omar's remarks about the treatment of American Muslims since the September 2001 terror attacks on New York and Washington.

Yet Omar's comments about US political backing for Israel being fuelled by money from a pro-Israel lobbying group led to criticism from both sides of the political aisle.

Pelosi used a meeting with Britain's opposition Labour Party leader Jeremy Corbyn on Sunday to speak out against anti-Semitism in politics.

She tweeted after the meeting that she and Corbyn discussed the importance of "protecting human rights, and the necessity of forcefully confronting anti-Semitism & Islamophobia".

Corbyn has been under pressure from Jewish groups to more thoroughly investigate and clamp down on anti-Semitic incidents involving Labour members.

But Pelosi also stuck up for Omar in her current standoff with Trump.

"I don't think any president of the United States should use the tragedy of 9/11 as a political tool," Pelosi said.