The singer was performing in Florida when the drink was thrown

A paper cup filled with "some sort of liquid" was thrown on stage but did not hit the singer, her publicist said.

Streisand, 64, shrugged off the protest, and told the Florida audience: "It's a free country. They're entitled to express their opinion".

The sketch, in which the singer trades insults with a Bush impersonator, has angered audiences in other US cities.

She was heckled on the opening night of her 20-city comeback tour and swore at an audience member during a concert in New York.

Media coverage

Streisand's manager, Martin Erlichman, said the sketch was supposed to be fun and would remain in the show.

"This skit has been so massively covered by media, it's impossible that it still could come as a surprise to any of the Bush admirers who bought tickets," he said.

In the sketch, President Bush is made to look foolish by saying things like "I'm concerned about the national debt, so I'm selling Canada".

The impersonator also asks whether he can sing a song with Streisand, who replies, "How about 'Enough Is Enough'?"

The singer is an outspoken liberal and supported Democratic Presidential candidate John Kerry in the 2004 elections.

She originally announced her retirement from touring six years ago, but has returned to the stage to raise funds for charity.