By Thomas Ferraro and Richard Cowan
WASHINGTON (Reuters) - Senate Judiciary Committee Chairman Patrick Leahy on Tuesday introduced a gay rights amendment to the Senate's immigration bill, prompting one of the measure's Republican sponsors to repeat his prediction that it would sink the legislation.
"It'll kill the bill" if it is included in the legislation, Florida Senator Marco Rubio said in a brief interview. "There is a coalition of groups who are supporting immigration reform who will not support it if that's in there."
Rubio, the son of Cuban immigrants and a possible Republican presidential candidate in 2016, is key to attracting conservative support for the bill. It remained uncertain whether the amendment would make it through the committee, which is controlled by Democrats.
Leahy could ultimately decide to delay the fight over the gay rights amendment for when the immigration legislation comes before the full Senate, instead of offering it in his committee.
The Leahy amendment, one of dozens offered two days before the committee takes up the bill, would allow U.S. citizens who are in "long-term committed relationships" to sponsor their foreign partners for green cards, which would allow them to live and work legally in the U.S.
"For immigration reform to be truly comprehensive, it must include protections for all families," said Leahy, a Democrat from Vermont. "We must end the discrimination that gay and lesbian families face in our immigration law."
Republicans in addition to Rubio have been warning Democrats for weeks that including the measure on same-sex couples would doom the immigration legislation in Congress.
Amendments to the controversial immigration bill flooded into the Senate Judiciary Committee, underscoring the long fight ahead before enacting one of President Barack Obama's legislative priorities this year.
The committee will begin debating the nearly 900-page bill on Thursday. Members of the panel had a Tuesday deadline for submitting ideas for amending the measure.
The Judiciary Committee is planning to spend most of this month debating immigration and supporters hope to send the bill to the full Senate by the beginning of June.
Once on the Senate floor, assuming the Judiciary Committee ultimately approves the measure, all 100 senators would then have a chance to offer amendments to the bill, which would be the first major overhaul of U.S. immigration law since 1986.
Senator Orrin Hatch of Utah, a senior Republican on the panel, has submitted 24 amendments that include moves to clamp down on the cultivation of marijuana on federal lands and requiring DNA identification for every adult illegal immigrant who could earn legal status under the legislation.
Some immigration advocacy groups already criticized the legislation for requiring stiff fees from immigrants here illegally and trying to become citizens.
Hatch wants to double one of the fees, to $1,000, for a "green card" providing permanent residency, the final step toward citizenship.
(Editing by Fred Barbash and Christopher Wilson)