White House officials are quietly urging Congress to give itself a "modest" 5.5 percent raise next month when most of the federal and military establishment gets a 7 percent boost. The idea is to make it possible for the Carter administration to give promised salary increases to thousands of government executives, who traded in much of their bureaucratic tenure and job rights for the promise of more exciting, and financially rewarding, jobs.

Members of the new SES (Senior Executive Service) were told they would be eligible for better pay, assignments and bonuses if they would leave the more secure GS (General Schedule) grade system to join the elite corps. The overwhelming majority of "supergraders" in GS 16 through 18 accepted SES status. Now they are waiting for the dollar rewards. But what they get depends on Congress.

SES has the authority to set rates for its members, but it cannot pay them unless Congress lifts the $47,000 career federal pay lid. Members aren't likely to do that unless they boost their own $57,500 salary.

An estimated eight of every 10 SES members lives and works in metropolitan Washington.

President Carter has okayed six new pay levels for the SES. They are $47,889, $49,499, $51,164, $52,884, $54,662 and $56,500. Those are the official rates. But they cannot be paid unless Congress lifts the career government salary ceiling.

Congress is in a bind because under law it is "due" two raises next month. One is the 7 percent for regular civil servants. The other is the 5.5 percent government raise of last year (1978) that Congress declined to take for both economic and political reasons. Insiders believe Congress will deny itself the 7 percent boost, but the White House hopes it will take the 5.5 percent of last year.

Congress can allow the 7 percent federal-military raise to go into effect simply by not vetoing it before the Sept. 30 deadline. Within the same time period Congress must do something about its own pay. Its options are to take both pay raises, the 5.5 percent and 7 percent; take only one of them; or take no raise at all.

The latter option -- which would be the most politically popular -- would mean federal career pay would remain frozen at $47,500 this year, and probably next year too since Congress doesn't vote pay raises in election years.

The rapidly approaching deadline and the political sensitivity of the issue are the reasons the White House is hoping Congress will take the middle ground and give itself a 5.5 percent raise and raise the government pay lid so SES members can get some of the bucks they signed on for.