UPDATE 5-Sanders and Warren defend progressive policies against attacks in U.S. Democratic debate

(Updates throughout)

By John Whitesides and Jarrett Renshaw

DETROIT, July 30 (Reuters) - Elizabeth Warren and Bernie Sanders offered an unabashed defense of their progressive policies during a Democratic presidential debate on Tuesday, as their more moderate rivals criticized their proposals as unrealistic and politically untenable.

The debate frequently pitted the two U.S. senators against the other eight candidates on stage, with healthcare and immigration policy highlighting the divisions between the two camps.

On the first night of back-to-back debates, Democrats were united in stressing the urgency of defeating Republican President Donald Trump in the November 2020 election. But they delivered bruising critiques of their party rivals' positions as detailed policy disagreements dominated the nearly three-hour event.

The dispute between the moderate and liberal wings of the Democratic Party highlighted the central question of the nominating contest: Which candidate in the field of more than two dozen would be best positioned to beat Trump next year?

The moderate wing, led at times by Montana Governor Steve Bullock, argued Democrats risk losing voters after moving too far to the left in the opening debate last month in Miami.

"Watching that last debate, folks seemed more concerned about scoring points or outdoing each other with wish-list economics than making sure Americans know we hear their voices and will help their lives," said Bullock, who emerged as a forceful voice in his first presidential debate.

In contrast, progressives argued their policies would excite voters and allow them to draw a distinct contrast to Trump.

Warren rebuked former U.S. Representative John Delaney, who often played the role of foil to the progressives during the debate, firing back at his criticism of her policies.

"I don’t understand why anybody goes to all the trouble of running for president of the United States to talk about what we really can’t do and shouldn’t fight for," she said.

Sanders also bristled at arguments that his proposals could not be realistically achieved, saying: "I get a little bit tired of Democrats afraid of big ideas. Republicans are not afraid of big ideas."

Trump has been eager to paint the entire Democratic field as socialists, seeking to make any eventual nominee unsavory for voters by arguing Democrats want to raise taxes, open the U.S. borders and take away private healthcare.

Trump's campaign spokeswoman echoed that sentiment in a statement about the debate on Tuesday night, calling the field "radical Democrats" with a "socialist message."