The Reagan administration will block any congressional attempt to eliminate or water down veterans preference procedures that give hiring breaks and added job security to former servicemen and women. Forty-four of every 100 federal workers are veterans, or benefit from veterans preference in some way.

The Carter administration sought to phase out veterans preference, arguing that it discriminates against women and, except in the case of disabled vets, had outlived its usefulness. The Supreme Court has upheld the constitutionality of veterans preference. Its importance is growing as many U.S. agencies prepare to make layoffs because of budget cuts.

On Wednesday this column reported that the White House soon would announce strong support for existing veterans preference rules. Yesterday, in testimony before a House Veterans Affairs subcommittee, Donald J. Devine, head of the Office of Personnel Management, said he and the president are "strongly committed to the veterans preference program because the government owes a special obligation to those who have been willing to sacrifice their lives in the service of their country."

Under the Veterans Preerence Act of 1944 (and subsequent laws) anybody honorably discharged from the military (with 180 days or more of service) since Dec. 7, 1941 (Pearl Harbor Day) is entitled to special consideration in federal employment, and greater job protection during RIFs, a government term for layoffs. That preference in some cases extends to the widows, children and mothers of veterans who died in service and to spouses of permanently disabled veterans.

Veterans applying for government jobs get 5 points to their test scores (if they first get a passing grade). Disabled vets get a 10-point preference. That means if a nonveteran and a veteran score 90 on a civil service exam, the veteran is considered to have scored 95. Disabled veterans and veterans are supposed to be listed at the top of federal job registers, ahead of nonveterans.

The same preference holds true for veterans during RIFs. Nonveterans are supposed to be laid off before regular veterans, who, in turn, are subject to layoff before disabled veterans.

Many low-paying, custodial and service jobs have been traditionally reserved for veterans. These include guards, messengers and custodial workers and -- in the few buildings that still have them -- elevator operators. wNonveterans may take the jobs if there are no veterans on job registers or if the veterans decline them.

The Carter administration -- spurred by former VA chief Max Cleland, who lost both legs and an arm in Vietnam -- tried to give maximum help to Vietnam-era vets, but overall it sought to phase out benefits for World War II and Korean conflict veterans, except the disabled. Idea was they have had plenty of time to take advantage of veterans preference. Various groups, especially women's rights organizations, have demanded that preference for veterans be severely limited to the disabled.

Veterans hold 44 percent of all federal jobs -- with heaviest concentrations in Defense, the Veterans Administration and the U.S. Postal Service. Twenty-nine percent are Vietnam era vets. Devine said yesterday that, since the Veterans Readjustment Act became law during the Nixon administration, 160,000 veterans have been hired by Uncle Sam in civilian jobs. Last year, he said, 10 percent (2,114) of the VRA hires were women and 40 percent were minorities.