NASHVILLE, Tenn. (AP) _ Looking to build momentum heading into his convention, Al Gore was set to collect a twin boost with the backing of a big labor union and an important police group.

The United Auto Workers union would issue an endorsement of Gore later this week, easing a thorny labor problem for Gore in some very important Midwestern battleground states, said Democratic sources speaking on condition of anonymity.

At the same time, Gore collected the formal endorsement of the National Association of Police Organizations, meeting at its convention in Washington. That move solidifies Gore's law-and-order credentials.

``The National Association of Police Organizations voted overwhelmingly to endorse Vice President Gore, primarily because he has earned it,'' said association president Thomas J. Scotto. ``This endorsement is based on his past performance and his unwavering support of the law enforcement community.''

UAW president Steve Yokich had split with Gore on trade issues, and the schism had deepened to the point where the big union was flirting with Green Party candidate Ralph Nader.

With thousands of members in important states like Michigan, that would have been a harsh blow to Gore's hopes.

But the union's leadership was meeting in executive committee in Michigan, and there was pressure growing to issue an endorsement of Gore. The sources said that formal endorsement was likely to come within the next three days.

While Gore has gotten overwhelming backing from organized labor, the split with the UAW has been painful and comes because that union differs strongly and passionately with Gore on trade policies.

The Clinton-Gore administration has backed a series of free trade efforts that the union argues amounts to shipping American jobs overseas.

Michigan is often viewed as an example of the damage the union could do to Gore if it strayed.

Polls have shown Gore and GOP rival George W. Bush in a head-to-head race in that battleground state, but Bush gets an advantage when Nader is factored into the race.