WASHINGTON, Apr 7 (Reuters) A U S Senate compromise on an overhaul of immigration law appeared to get bogged down late in the face of opposition by some Republicans who say it would give amnesty to lawbreakers.

It appeared unlikely the Senate would approve before a two-week congressional break today the radical immigration reform that would give millions of illegal immigrants a chance to earn U S citizenship.

The bill's backers yesterday expressed fear that failure to enact the legislation before lawmakers leave for their spring break could hurt its chances in a congressional election year.

Senate Republican Leader Bill Frist of Tennessee and Senate Democratic Leader Harry Reid of Nevada earlier hailed a ''breakthrough'' on the compromise bill that would include a guest worker program sought by President George W. Bush.

But the two leaders were unable to agree on how many amendments to the bill would be allowed.

Frist later accused Democrats of trying to block the bill by refusing to allow amendments. Democrats said they wanted to protect the bill from being ''gutted'' by Republicans opposed the bill.

''Republicans are still deeply divided on this issue, and we must protect this from those senators bent on gutting the bill with hostile amendments,'' said Reid.

The congressional debate over how to deal with an estimated 11 million illegal immigrants has sparked large protests in many U S cities against a crackdown and more demonstrations are planned in 10 cities on Monday.

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