Senate Democrats and a top Obama administration official sought Wednesday to decouple border security from a pathway to citizenship for illegal immigrants, a centerpiece of the principles laid out last month by a bipartisan Senate working group.

“There are still some stuck in the past who are repeating the demands of ‘enforcement first,’ ” Senate Judiciary Chairman Patrick J. Leahy, D-Vt., said at a committee hearing on immigration. “I fear they mean ‘enforcement only.’ To them I say that this has stalled immigration reform for too long.”

Homeland Security Secretary Janet Napolitano agreed.

“Too often, the ‘border security first’ refrain simply serves as an excuse for failing to address the underlying problem,” she said. “It also ignores the significant progress and efforts we have undertaken over the last four years.”

Napolitano also endorsed a tough employment verification system to reduce the incentive for immigrants to arrive illegally.

“If we have extra money to invest in immigration enforcement, is it better spend on more border patrol agents or is it better spent investing in a worker verification program that really looks at the demand side of this issue?” she asked.

Those positions could conflict with the Senate working group’s efforts. In its proposal, the so-called “gang of eight” laid out a plan in which the path to citizenship would only open up once a commission consisting of border state officials certifies that the border is secure.

But Democrats have since described the commission as more of a formality, saying it would not hold up the process of granting citizenship to undocumented people.

Sen. Jeff Flake, R-Ariz., a member of the bipartisan group, also said he did not want the issue of border security to derail the whole measure.

“I do want to get immigration through,” Flake said. “I don’t want any of the elements that we need to finish to hold up any of the other elements.”

Leahy said he plans to mark up an immigration bill in the committee within the next few months and move it onto the floor, warning that “our window of opportunity will not stay open long.” President Barack Obama has praised the Senate group’s work, while also making clear that he would put his own plan forward if lawmakers fail to reach a consensus.

Sen. Charles E. Schumer, D-N.Y., a member of the bipartisan group, said the talks have been productive and that the members are committed to sticking to their timeline of releasing a bill next month.

“We know we can’t take forever to get this done and we’re on track,” Schumer said. “Both sides know they have to give and they are.”

A similar bipartisan group in the House is also working on a proposal but could face more roadblocks. Many House Republicans have said they would not support granting citizenship, a precondition for Democrats. That could imperil the negotiations in that chamber.

Senate Republicans were more upbeat at Wednesday’s hearing but emphasized that enhanced border security would have to be part of any overhaul in order to garner their support. The last time Congress approved a major immigration overhaul, in 1986, the border security and employment verification provisions were never properly enforced, they said.

When Congress tried to tackle immigration in 2007, the measure collapsed in the Senate, in part because of concerns about border security, said Sen. John Cornyn, R-Texas.

“The reason immigration reform failed in 2007 is that the American people don’t actually believe that Congress will actually follow through on important measures like border security, employment verification, visa overstays and the like,” Cornyn said.

But it won’t be easy. Sen. Jeff Sessions, R-Ala., was sharply critical of the idea of making it easier for illegal immigrants to work legally and of opening up the borders to more foreign workers in the future. Such steps could put American workers at risk and drive down wages, he said, while suggesting that immigration advocates in the business community are looking for cheap labor.

“There’s a lot of overconfidence about this bill,” Sessions said. “If it doesn’t really work, it’s not going to pass.”

Napolitano said the administration has already improved border security in the past four years. Last year, officials deported 410,000 people, more than in previous years. Border apprehensions, a common way to measure the inflow of illegal immigrants, are at a 40-year low, she said.

She added that the administration will have an enhanced visa monitoring system by the end of the year to better track when visa holders enter and leave the country. Right now, roughly 40 percent of illegal immigrants are thought to be people who came legally but overstayed their visas.

Democrats also emphasized that any immigration measure should make it easier for high-tech workers and for relatives of legal permanent residents to stay in the country. Leahy said he wants to include provisions protecting same-sex couples as well as victims of domestic violence who could lose their legal status if they leave their abusive spouse.

Later Wednesday, a key Republican member of the Senate group criticized Napolitano’s position and reiterated that tougher border security is a prerequisite to any immigration deal. Sen. Marco Rubio, R-Fla., said Napolitano’s statements at the hearing were “discouraging for those of us who are serious about permanently fixing America’s immigration system.”

“By continuing to oppose a key security principle with bipartisan backing, Secretary Napolitano and this administration appear to be laying the groundwork to scuttle the bipartisan effort in the Senate,” Rubio said.