By David Lawder and Rachelle Younglai
WASHINGTON (Reuters) - U.S. Senate leaders are working to craft legislation by Sunday that averts the year-end "fiscal cliff" of tax hikes and spending cuts, but many details needed to be worked out after a crucial meeting with President Barack Obama on Friday.
U.S. Senate Democratic leader Harry Reid and his Republican counterpart Mitch McConnell, termed the meeting "constructive" and "positive" and said they would keep working on trying to find a solution over the weekend.
After adjourning on Friday, Reid he would probably not call the Senate back into session until about 1 p.m. EST/ 1800 GMT on Sunday to give leaders time to hash out a deal.
"We are engaged in discussions, the majority leader and myself and the White House, in the hopes that we can come forward as early as Sunday and have a recommendation that I can make to my conference and the majority leader can make to his conference," McConnell said on the Senate floor.
"So we'll be working hard to try to see if we can get there in the next 24 hours. So I'm hopeful and optimistic," he added.
An aide to House of Representatives Speaker John Boehner said it was agreed at the White House meeting that the Senate should act first.
"The speaker told the president that if the Senate amends the House-passed legislation and sends back a plan, the House will consider it - either by accepting or amending," the aide said.
However, Reid said it would be difficult to craft a solution that can win passage in both the House and Senate, adding that it involves "big numbers."
"Whatever we come up with is going to be imperfect," Reid said. "Some people aren't going to like it. Some people will like it less. But that's where we are and I feel confident that we have an obligation to do the best we can."
(Reporting By David Lawder, Rachelle Younglai; editing by Christopher Wilson)