San Antonio Mayor Julian Castro (D), an ally of President Obama's, said the administration needed to revise its deportation policy.
"My hope is that just like he did with [easing childhood deportations], the president will find ways that are within his power, that are constitutional, to ease the level of deportations," Castro continued.
The three-day event at the University of Texas is being held to mark the 50th anniversary of the Civil Rights Act of 1964, and will feature speeches from President Obama as well as from three former presidents.
Castro is a rising Democratic star and has quickly become a leading voice for immigration reform since Obama gave him the keynote speech at the Democratic National Convention in 2012. His twin brother, Julian Castro, was elected to Congress in 2012. The issue of deportation has become a flashpoint on the left.
Former Mississippi Gov. Haley Barbour (R), another advocate for immigration reform, said on the panel he thought House Speaker John Boehner (R-Ohio) was serious about getting immigration passed but didn't yet have the votes from House Republicans.
He also said GOP worries that President Obama wouldn't enforce the law were pointless.
"You can like President Obama or not like President Obama. That's not the issue. By the time this gets going he's not going to be the president anymore, so let's talk about the real issues that need to be dealt with. I assume the law is going to be enforced if done right," he said.