WRAPUP 4-Clinton, Obama go on attack ahead of crucial vote

(Adds Obama comments from Scranton rally, edits)

By Jeff Mason

JOHNSTOWN, Pa., April 20 (Reuters) - With two days to go before a crucial U.S. presidential vote, Democrats Barack Obama and Hillary Clinton sharpened their attacks on Sunday, with Clinton pouncing on Obama for saying Republican John McCain would be better for the country than George W. Bush.

Obama told a rally in Reading, Pennsylvania McCain would be an improvement over Bush, a comment that seemed to undercut the message he often pushes that electing McCain would amount to giving the current Republican president a third term.

"You have a real choice in this election -- you know, either Democrat would be better than John McCain, and all three of us would be better than George Bush," Obama said.

Clinton, vying with Obama for the Democratic nomination and the right to run against presumptive Republican nominee McCain in the November election, criticized Obama's comments.

"We need a nominee who will take on John McCain, not cheer on John McCain," she said at a rally in Johnstown.

The two candidates sparred ahead of Tuesday's Pennsylvania primary, which has become a major test in the race for the party's nomination.

Clinton, a New York senator who needs a win in the state to keep her presidential ambitions alive, leads in polls but Obama, an Illinois senator and the national front-runner, has cut into her one-time double-digit lead in recent weeks.