The House is moving toward a vote on a bill aimed at securing the U.S. border with Mexico, as majority Republicans seek to demonstrate that they can chart their own course on immigration -- not just oppose President Barack Obama.

The legislation passed the House Committee on Homeland Security late Wednesday on a party-line vote of 18-12 and party leaders said it would come to the floor next week.

"For God's sakes, if we can't unite around border security what can we unite around?" said Rep. Michael McCaul of Texas, the committee's chairman.

But it remained uncertain whether House Republicans would unite around McCaul's bill, as conservatives who have scuttled past attempts by GOP leaders to deal with immigration expressed concerns that the legislation does too little to stem illegal immigration.

Several also groused that leadership was trying to rally support for the border security bill instead of making a strong stand against recent executive actions by Obama granting relief from deportation to millions.

The border bill "is a show horse, not a work horse, and as such it is an effort to convince the American people that we are doing something substantive to secure the border when in fact nothing substantive is being done," said Rep. Mo Brooks, R-Ala.

Democrats, meanwhile, said the bill was filled with unrealistic mandates that would make it harder for border agents to do their jobs while spending $10 billion on an array of drones, surveillance systems, radar, fencing and other technologies that might do little real good.

"It is overly prescriptive and it is impossible, operationally, to succeed," said Rep. Sheila Jackson Lee, D-Texas. "This bill militarizes the nation."

The bill would require operational control of high-traffic areas of the border within two years, and operational control of the full border within five years. The bill defines operational control as stopping or turning back all attempted border crossers, which Democrats said was unrealistic. Some past immigration and border bills, including one advanced in the last Congress by McCaul's committee, have sought to block 90 percent of would-be crossers.

McCaul's earlier border bill won unanimous Democratic support by leaving it up to the administration to come up with a strategy to secure the border. This time he abandoned Democrats to write a bill designed to be tougher and win more GOP support.

It comes as a number of rank-and-file congressional Republicans are eager to advance immigration legislation of their own and hope a border bill will be just a first step. Immigration overhaul legislation stalled in the House in the last Congress because of conservative opposition. Now some Republicans want to show they can offer solutions to the pressing national issue, especially heading into the 2016 presidential election where the Latino vote could be critical.

"It's incredibly frustrating to absorb, continue to absorb, the whacks on doing nothing on the issue," said Rep. Mark Amodei, R-Nev. "I'm just tired of defending nothing, I can't defend nothing."

Obama cited House inaction as he took unilateral steps in November to offer deportation relief and work permits to some 4 million immigrants here illegally, a move that infuriated Republicans.

House Republicans attached language to a must-pass spending bill for the Homeland Security Department last week to block Obama's move, but the measure faces near-certain death in the Senate, leaving Republicans still searching for a way to stop the president. That issue is certain to complicate any immigration legislation Republicans seek to advance.