Because of a standoff between key players on House and Senate Budget committees, Congress is heading into one of its most critical periods on the federal budget with a power vacuum at the Congressional Budget Office.

The CBO, a nonpartisan agency of Congress that plays an important role in providing lawmakers and staff with independent economic and budget analyses, has been without a director for nearly a year, when Rudolph G. Penner resigned. Between his departure last March until December, the agency was headed by an acting director, Edward M. Gramlich.

But Gramlich, who was one of six finalists for the director's post, left the CBO Dec. 18 to return to an academic position at the University of Michigan. The acting directorship was then filled by James L. Blum, who also continues in his previous position of assistant director for budget analysis. Meanwhile, another top position, assistant director for fiscal analysis, has also become vacant.

Congress' failure to find a permanent replacement for Penner stems from a number of factors, including a protracted struggle with the White House last year over the budget, which kept the leadership of the budget committees occupied by such things as revising the Gramm-Rudman-Hollings budget law and last fall's summit conference on deficit reduction with the administration.

But the major reason for the post going vacant is a dispute between House Democrats led by House Budget Committee Chairman William H. Gray III (D-Pa.) and the leadership of the Senate Budget Committee. Though the CBO director is formally appointed by the speaker of the House and majority leader of the Senate, they usually simply ratify the consensus choice of the chairmen and ranking minority members of the two budget committees.

Gray, with the backing of House Speaker Jim Wright (D-Tex.), has backed the House Budget Committee's chief economist, Van Doorn Ooms, for the position. But Gray's choice has met stiff resistance from the Senate committee chairman, Lawton Chiles (D-Fla.) and ranking Republican, Pete V. Domenici (N.M.), because they feel that the choice of someone associated with the majority side of the House panel could give the appearance of a partisan tilt at the agency.

"The worst thing they could do is put someone in who is perceived as in the hip pocket" of the House Democratic leadership, said one congressional aide who asked not to be identified.

Another Capitol Hill staff member said that Ooms -- who holds a Ph.D. from Yale, was a Rhodes Scholar and worked during the late 1970s on the Senate Budget Committee -- is well respected, but could still be viewed as someone who might favor both the House and the Democratic majority in a position that depends on its reputation for nonpartisanship.

Gray has reportedly argued privately that his Senate counterparts have changed the criteria in order to block Ooms' appointment, pointing out that Penner -- who came to the CBO from a think tank -- had served previously in Republican administrations without bringing a partisan taint with him.

Gray declined to discuss specific candidates, but said, "I don't think any one person should not be considered because of previous employment." Neither Chiles nor Domenici were available for comment.

Though it is difficult to assess the impact of the CBO vacancy, Gray said it could cause a "reluctance to make decisions . . . there might be hesitation, ambiguity."

Although the selection committee is scheduled to meet next week, any decision will likely come too late to effect one of the CBO's critical functions, reporting to the budget committees next week on its economic and deficit projections.

History: The Congressional Budget Office (CBO) was created in 1974 under the Congressional Budget and Impoundment Act, the legislation that defined and organized the budget process used today.

Purpose: CBO provides Congress with key economic and budgetary information, completes cost estimates and program analysis.

Staff: Current staff ceiling of 226.

Budget: Fiscal year 1988 budget is $17.8 million.

Directors: Alice Rivlin, 1975-83; Rudolph G. Penner, 1983-86.