Sen. William L. Scott (R-Va) reversed an earlier decision yesterday and said that he will resign Monday to give Republican Sen-elect John W. Warner an edge in seniority over most other freshment senators.

Gov. John N. Dalton immediately announced that he will appoint Warner to serve the remainder of scott's term-1 1/2 days.

Without the resignation, Warner would have been sworn into the Senate for the first time at noon on Jan. 3. Since Scott's resignation will become effective at midnight Monday, Warner will be able to take office Jan. 2.

The office of the secretary of the Senate said that at least three others of the 20 newly elected senators will benefits from early resignations by their predecessors, but Warner will have an edge in seniority over the rest.

Seniority determines ranking on Senate committees and could be crucial to Warner in getting desirable appointments in later years.

Scott had said earlier that he would serve out his full Senate tern and his decision had been supported by state GOP chairman George N. McMath as "proper."

However, the controversial senator, who did not seek reelection to a second term, said in an interview yesterday that he changed his mind because "I didn't want Virginia to be at any disadvantage" in seniority.

He said he had read of intentions by other retiring senators to resign early to help their successors and decided after conversations with his wife, Inez, and their three children to do the same.

Doath commended Scott in a statement "for this act of courtesy to both Sen-elect Warner and all Virginians."

Warner issued a statement through press secretary William Kling saying. "We're very pleased by this decision because it's good for Virginia and Virginia's people."

Scott said he is spending his last days in officeie completing the packing of records for transfer to the library at George Mason University, which will have custody of the papers from his 12 years in Congress.

Scott served three terms in the House of Representatives from the old 8th Congressional District before being elected to the Senate in 1972 in an upset over former Sen. William B. Spong, a Democrat.

Scott said his decision to step down just before the end of his term was not prompted by appeals from anyone else, including Warner. He said he had met with Warner before Christmas but had not discussed an early resignation with him.