WASHINGTON (AP) _ Some Iraqi military units are being forced to go four days without water, and some are being given salt water to drink, a Pentagon spokesman said Thursday.

''I think it's safe to say that we are getting growing evidence that it's a very unhappy lot,'' Capt. David Herrington said of Saddam Hussein's forces.

Herrington, deputy director of intelligence for the Joint Staff, said at a Pentagon briefing he could not confirm reports of defections among the elite Republican Guard. But he said the unit does appear to be acting as a barrier to Iraqi troops attempting to return home from units in the south, occupying Kuwait.

The 150,000-man Guard is Saddam's best-trained and equipped force, and has been a focus of the allied bombing campaign. It is located near the Kuwait- Iraq border to repel any allied ground campaign that could push into Iraqi territory.

Herrington said the allies have received information that some of the Iraqi forces ''go for as much as four days without potable water, that sometimes they are provided salt water to drink.''

The Navy captain said such information leads the Pentagon to believe that ''a large number'' of Iraqi soldiers are defecting northward, and that only ''a very insignificant number'' has tried to move south across the border into Saudi Arabia.

''If there is a significant defection, it is going north,'' Herrington said.

''There are clearly some means put in place to stop them from going north, and that's the execution squads and the Republican Guards that are in behind all those forces,'' the Navy captain said.

Allied commanders in Riyadh, Saudi Arabia, have reported in weeks past that so-called ''execution squads'' have attempted to halt the flow of desertions by killing soldiers who try to leave their units.