A joint Senate-House conference commmittee agreed yesterday to put off a decision on the proposed controversial extension of the west front of the Capitol until next year.

The decision followed a pattern that has become familiar during the past decade, with the House repeatedly voting to expand the building and the Senate pushing to repair its deteriorated sandstone walls.

The same kind of standoff occurred again yesterday when the conference committee met to resolve differences between the House and Senate versions of a bill that would provide about $1 billion to operate Congress and several related agencies during the 1978 fiscal year.

On June 29, the House voted, 212 to 204, to put $55 million into the bill for an extension of the west front, the facade of the Capitol that faces the Mall and downtown Washington. The Senate, without a specific roll can on the issue, voted Monday to ask Capitol Architect George M. White to obtain plans and estimates for restoration.

The extension plan, opposed by the American Institute of Architects, call for covering the last remaing visible section of the original 177-year-old Capitol building. The old walls would remain standing inside the expanded building.

The center of the structure, immediately below the dome, would be extended about 22 feeto 60 feet, filling in courtyards. The outside wings of the building used by the two chambers of Congress for their sessions would remain unchanged.

Yesterday, House conferees, headed by Rep. George E. Shipley (D-III), agreed to the Senate request for preparation of restoration plans. Senate conferees, healed by Sen. Walter Huddleston (D-Ky.), agreed to instruct White to obtain detailed plans and estimates for the extension, assuring it equal status for future consideration.

"It seems to me that what we are doing is just putting it off," Rep. William L. Armstrong (R-Colo.) observed.

Rep. Lawrence Coughlin (R-Pa.) offered his tongue-in-cheek compromise to Huddleston: "We'll extend the House side and restore the Senate side."

The strongest plea for the extension was voiced by Rep. Bob Traxler (D-Mich.). The Capitol, he said, is a "living" building, not just a historic place, and it should be maintained for efficient operations of Congress.

In another action, conferees agreed not go grant $225,000 voted by the Senate to continue restoration of the old CongressiD.C. General Hospital.*