"I hope this body can seize this opportunity and deliver real progress," Senate Majority Leader Mitch McConnell, a Kentucky Republican, said.
Days of freewheeling debate are expected as a deadline draws near for hundreds of thousands of young immigrants brought illegally to America as children. Last year, President Donald Trump terminated Deferred Action for Childhood Arrivals, which temporarily protected young immigrants from deportation, and gave Congress until March 5 to enact legislation addressing their legal status.
Trump has proposed granting DACA beneficiaries a path to eventual U.S. citizenship, something backed by large majorities of lawmakers from both political parties. But he has also insisted on constructing a wall along the U.S.-Mexico border, reducing the number of legal immigrants America accepts, and prioritizing newcomers with advanced work skills.
Senate Republicans unveiled a proposal, the Secure and Succeed Act, that encapsulates the White House's blueprint for immigration.
FILE - Senate Majority Leader Mitch McConnell, R-Ky., leaves the chamber after announcing an agreement in the Senate on a two-year, almost $400 billion budget deal, at the Capitol in Washington, Feb. 7, 2018.
"I support the president's proposal and my [Republican] colleagues' proposal to implement it," McConnell said. "The Secure and Succeed Act is fair, addresses both sides' most pressing concerns, conforming to the conditions the president has put forward."
Any immigration proposal will need three-fifths backing to advance in the Senate, where Republicans have a slim one-seat majority. Democrats signaled the Republican immigration plan is a non-starter.
"The key is to find a consensus bill largely acceptable to significant numbers of members in both parties," Minority Leader Chuck Schumer, a New York Democrat, said. "The only enemy here is overreach. Now is not the time nor the place to reform the entire legal immigration system. Rather, this is the moment for a narrow bill."
FILE - Senate Minority Leader Chuck Schumer of N.Y., center, accompanied by Sen. Bob Casey, D-Pa., at left, speaks on Capitol Hill, Feb. 6, 2018 in Washington.
Democrats and some Republicans have suggested limiting an immigration bill to a DACA fix and border security enhancements.
That, too, is unlikely to succeed, according to California Democrat Dianne Feinstein.
"There will probably be at least three bills," Feinstein told VOA. "The first would likely be a Republican bill; the second, a Democratic bill. They will probably both go down [to defeat], and then maybe the third bill will be the compromise."
A compromise bill could come from a working group of Senate moderates from both political parties. Led by Maine Republican Susan Collins, the group helped forge an end to last month's three-day partial federal shutdown.
"I think it [Senate passage of an immigration proposal] is doable," Collins told VOA. "We're working on our bipartisan, common-sense coalition proposal, which I expect we will be releasing later this week."
The Senate will consider individual immigration proposals as amendments to an uncontroversial bill that will serve as a legislative vehicle for immigration reform.
"It's a topic we've been discussing for the last years," Republican Sen. John Barrasso of Wyoming said. "So, I'm expecting to have a very spirited debate and then votes - whoever gets to 60 votes wins."
"I'm not sure what's going to happen, because it's been so long since we tried this [reformed U.S. immigration]," Illinois Democratic Sen. Dick Durbin said. "But it is exciting to think that men and women elected to this body, known as the 'greatest deliberative body,' are finally going to deliberate."
"Seventy or 80 percent of the American people, including me, agree that kids who grew up here that haven't gotten in bad trouble [with the law] not only should be able to stay, but we have a vested interest in wanting them to stay and be part of a growing economy and a vibrant society," Missouri Republican Sen. Roy Blunt told VOA. "And 70 percent of the American people think we should be doing a better job at the border. Surely those two things can come together in a piece of legislation that winds up on the president's desk."
To become law, any bill the Senate passes would also have to be approved in the House of Representatives and get Trump's signature.