(CNN) – Democratic Sen. Patrick Leahy filed three amendments Tuesday night to the immigration reform package, including a controversial amendment involving gay rights that could potentially derail the bill's progress in the Senate.
The senator from Vermont proposed recognizing same-sex marriages in which one spouse is an American, saying the amendment would "remove discrimination from our immigration system."
"Seeking equal protection under our laws for the LGBT community is the right thing to do," Leahy said in a statement announcing the amendments.
It's unclear whether the Senate will vote on the amendment, but the proposal virtually has no chance of winning the 60 votes almost certainly needed to clear the 100-member chamber.
The senator first proposed the legislation when the Senate Judiciary Committee marked up the bill last month. With vigorous opposition from some Republicans and some Democrats saying they wouldn't support the amendments, Leahy ultimately withheld his proposals.
However, he indicated he may bring them back up again. After the full Senate voted Tuesday to proceed with the bill, Leahy did just that.
"As the entire Senate turns to debate the immigration bill, the fight for equality must go on," he added in the statement.
Florida Sen. Marco Rubio - the most prominent Republican in the "Gang of Eight," a group of senators who developed a bipartisan proposal - was among those who called Leahy's amendments a poison pill virtually certain to destroy GOP support for the measure.
"I hope we can avoid this," he said last month during committee markup. "This is not the issue to engage this in, or you will threaten the entire product."
Rubio threatened to remove his own support from the bill if the same-sex marriage measure stayed.
Leahy also proposed two other amendments Tuesday that did not involve gay rights. One seeks a “reliable” process for foreign performers needing to gain entry to attend American non-profit performing arts organizations, while the other calls for extending benefits to a child or spouse of immigrants who hold agricultural temporary work visas.
– CNN's Ted Barrett, Alan Silverleib and Ashley Killough contributed to this report.