The Senate's top Republican said Sunday he could not predict whether stalled immigration legislation will pass, citing questions among conservatives as to whether it guarantees amnesty to illegal immigrants.

"It's a mixed picture," said Sen. Mitch McConnell, R-Ky., who called the vote, which is expected before lawmakers begin their Fourth of July vacation, too close to call. "There are good things in the bill, and not so good things in the bill."

McConnell and Majority Leader Harry Reid of Nevada last week said they planned to revive the legislation after critics of the measure initially succeeded in sidetracking it. The decision came after President Bush made a rare visit to the Capitol for a meeting with Republican senators, where he urged them to give the bill a second chance.

The legislation has generated intense controversy, particularly for provisions that could lead to eventual citizenship for many of the estimated 12 million immigrants now in the country unlawfully.

On Sunday, McConnell said several Republicans were disappointed with provisions involving the so-called Z-visa, which provides a means for illegal immigrants to gain interim legal status.

On the other hand, support for bill provisions that would boost money for border security is strong, he said.

"When we get to final passage, it's hard to know whether the votes will be there to pass it or not," McConnell said. "We'll finish Senate consideration of the immigration bill one way or the other."

McConnell made the comments on CBS "Face The Nation."