(Adds endorsements of Biden in Missouri, recasts with Biden "bloodbath" comments, adds LOS ANGELES to dateline)

By Michael Martina and Tim Reid

DETROIT/LOS ANGELES, March 7 (Reuters) - U.S. Democratic presidential candidates Joe Biden and Bernie Sanders will campaign in the Midwest on Saturday, as the two prepare for a showdown in Michigan, Missouri and four other nominating contests next week.

Sanders, 78, who until recently was the front-runner in the party's race to face Republican President Donald Trump in November, is now trailing in delegates and desperate to regain momentum after Biden, 77, received a rush of endorsements from party establishment figures following his strong "Super Tuesday" showing this week.

Below is what is happening on Saturday:

BIDEN WARNS AGAINST PRIMARY 'BLOODBATH'

After Sanders, a self-described democratic socialist, ramped up his attacks on Biden on Friday, Biden told a crowd at a fundraiser in Bethesda, Maryland, he was worried his battle with Sanders for the Democratic nomination could turn ugly.

"What we can't let happen is let this primary become a negative bloodbath. We can't tear this party apart and re-elect Trump. We have to keep our eyes on the ball," Biden said as he telephoned in to the Bethesda event.

Sanders, a U.S. senator from Vermont, had assailed Biden's record on trade, Social Security, gay rights and abortion on Friday - although he did promise to support the former vice president if he becomes the nominee.

The race has become a two-man contest between Biden and Sanders. Tulsi Gabbard, a Hawaii congresswoman, is the only other Democratic candidate still in the nominating contest, but has virtually no chance of winning.

Biden and Sanders will face off on Tuesday in Idaho, Mississippi, Missouri, Washington state, North Dakota and Michigan. A big win for Biden in delegate-rich Michigan would deliver a major blow to Sanders' hopes of becoming the nominee.

Showing continued momentum following his Super Tuesday wins, Biden's campaign said on Friday it had raised about $22 million in five days.

BIDEN WINS DOZENS OF ENDORSEMENTS IN MISSOURI

The moderate wing of the Democratic Party has been rapidly coalescing around Biden to stop a Sanders nomination, since Biden's big win in South Carolina on Feb. 29. On Saturday morning the Biden campaign announced another slew of endorsements from Democratic lawmakers in Missouri - over 60.

Missouri is one of six states to vote on Tuesday, where Biden was due to hold two events on Saturday. Jay Nixon, the state's former Democratic governor, swung his support behind Biden, leading a well-choreographed army of Missouri officials - 68 in all - to come out in support. They included current and former state politicians, judges, council members and aldermen.

Biden was due to campaign on Saturday in St. Louis and Kansas City, Missouri, where he is scheduled to be joined by U.S. Representative Emanuel Cleaver of Missouri, a former Congressional Black Caucus chairman who endorsed Biden in September.

SANDERS FOCUSES ON MICHIGAN

On Saturday, Sanders begins a weekend of campaigning in the crucial battleground state of Michigan, which offers 125 of the 1,991 delegates needed to win the nomination.

Sanders, who won the Michigan primary in 2016 when he ran unsuccessfully for the nomination against Hillary Clinton, will hold a rally in the Detroit suburb of Dearborn, and a town hall focused on racial and economic justice in Flint. On Sunday he is set to visit Grand Rapids and Ann Arbor.

Speaking to a crowd of more than 6,000 in downtown Detroit on Friday, Sanders continued to assail Biden for voting for the war in Iraq and trade deals, including the North American Free Trade Agreement, which he said had cost millions of American jobs in Michigan and other battleground states.

"Now, if we are going to defeat Trump in Michigan, Pennsylvania and Wisconsin, it will be very hard for a candidate who voted for these disastrous trade deals," Sanders said.

Sanders questioned whether Biden could generate enough energy and enthusiasm to prevail against Trump. But he also called Biden a friend, and said both were in agreement that they would support the other against Trump should the other win the nomination.

(Reporting by Michael Martina in Detroit, Tim Reid in Los Angeles and Trevor Hunnicutt in New York Editing by Edwina Gibbs and Matthew Lewis)

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