A Republican senator asserted Tuesday that President Donald Trump's immigration plan is the only measure that could pass Congress.
Sen. Tom Cotton of Arkansas spoke as the Senate was scheduled to start an open debate on how to proceed.
Bipartisan senators will continue contentious discussions on the best measure to protect up to 1.8 million young immigrants brought to the United States illegally as children and boost border security. A measure drafted by GOP senators including Cotton aims to mirror Trump's immigration proposal, which calls for restrictions on legal immigration that Democrats consider unacceptable.
"The president's framework bill is not an opening bid for negotiations. It's a best and final offer," Cotton told "Fox and Friends" on Tuesday morning.
The Senate will have an open process this week to propose amendments to include in an immigration bill. Measures will need 60 votes to pass. If all 51 Republican senators support Trump's framework, they will need nine Democrats to pass it.
Lawmakers are seeking legislation to enshrine protections for the young immigrants who were protected or eligible for the Obama-era Deferred Action for Childhood Arrivals. Trump ended DACA in September with a six-month delay.
While the program was originally set to start phasing out on March 5, pending lawsuits mean the deadline no longer holds. Still, Congress has sought to quickly seek a resolution to end uncertainty for the immigrants.
In a tweet Tuesday, Trump said "this will be our last chance" to "solve the DACA puzzle."
On Monday, Senate Majority Leader Mitch McConnell said he supported the proposal put forth by the GOP senators. It protects up to 1.8 million immigrants and offers them a path to citizenship. It also would put more funding toward border security, limit extended family migration and end the diversity visa "lottery" system.
Republicans argue the plan is the only one with a chance of passing the more conservative House and getting Trump's signature. Democrats have rejected it.
On Tuesday, Senate Minority Leader Chuck Schumer said finding a bipartisan compromise to shield the young immigrants and boost border security "should be the focus of all of our energies." He argued that the Senate could "take the lead" on drafting a bipartisan plan as it did with a recent budget agreement.
"It's still hard, we're not there yet, but we can get something done. Let's work toward that," he said on the Senate floor.
On Monday, Schumer called for a "narrow bill" rather than an overhaul of the immigration system.
Last month, Trump flatly rejected a bipartisan proposal brought to him by Sens. Lindsey Graham, R-S.C., and Dick Durbin, D-Ill.
Trump has proven difficult to pin down on immigration, and senators on both sides of the aisle have been frustrated with the process of striking a deal with him. Last month, only days after he told bipartisan lawmakers he would sign a compromise that can pass Congress, he retrenched and pushed for his own plan.
Democrats aim not to alienate an energized liberal base, which wants a quick resolution to DACA protections and opposes Trump's pledges to crack down on immigration and build a wall along the Mexican border. Many House Democrats, and some of the party's lawmakers in the Senate, held out on supporting a massive bipartisan budget deal last week because of immigration.
Trump, meanwhile, does not want to anger his supporters who cheered his push to limit immigration. Conservative House Republicans will also be reluctant to back a bill that does not include restrictions on legal immigration.