A bipartisan bill aiming to revise employee pay guidelines for Border Patrol agents could add "nearly 1,500? more agents to deal with a sudden humanitarian crisis of thousands of undocumented immigrants surging across the southern border, agency officials said today.

The proposed legislation, championed by Sens. John McCain, R-Ariz., and Jon Tester, D-Mo., would change the pay structure of the Border Patrol to allow managers wiggle room around existing budgetary restraints on overtime wages. Agency officials say the existing system puts too much of a strain on their budget, forcing the agency to pull officers off the line rather than allow the extra hours.

"That would give us more capability," Border Patrol Deputy Chief Ronald Vitiello told the Senate Homeland Security Committee. "It's in essence giving us nearly 1,500 agents more capability along the borders with current staffing levels."

The bill would create flexibility in the budget "so I don't have to shrink hours in order to reduce those payments," Vitiello added.

A sudden increase of undocumented immigrants streaming out of Central America into the Rio Grand Valley in the past month has created overcrowding and deteriorating conditions at detention and holding facilities, officials said. The influx has included hundreds of children, a 90 percent increase over the same time last year.

Today's hearing came hours after the Pentagon announced it would be opening a third military base to house the thousands of minors going through processing this year. By law, the Department of Health and Human Services cares for the undocumented youth but dwindling resources has now forced the administration to lend auxiliary housing at Lackland Air Force Base in Texas, Naval Base Ventura County in California, and now Oklahoma's Fort Sill.

READ MORE: Obama Calls Surge of Children Across US Border, "Urgent Humanitarian Situation"

The estimated 1,500 additional officers from the bill was reduced slightly by a followup statement from Brandon Judd, whose labor union governs some 17,000 agents. But the gist of the argument was the same.

"In essence, you'll be paying me the same amount of money to work 10 hours as what you're currently paying me to work 9.3 hours. And that's where the additional 1,000 to 1,200 agents comes in," the president of the National Border Patrol Council said, responding to questions from committee chairman Sen. Tom Carper, D-Del.

The nuggets fell off the tail of nearly two hours of budgetary questioning around Border Patrol wages, which came under fire in 2013 when an Office of Special Council report found employees were abusing the system to double-dip overtime pay privileges.

Vitiello also said that past attempts by the agency to reduce man hours during last year's across-the-board federal spending cuts known as the sequester came with "fair" results for the risk, but the current humanitarian crisis meant it was no longer a feasible option.

"You're reducing capability," he said. "Now we think that those risks that we were taking are adequate, and substantial, but manageable. And in the situation … we recognize now that that can't be the way forward."

Judd concurred, adding the influx and current pay constraint created a domino effect across the border.

"It's pulling agents out of the field. They're no longer patrolling the border," he said. "They're having to deal with this whole influx of minors that are coming in. They're having to process them. They're having to watch them. They're having to feed them. They're having to do all these different things instead of actually being out and patrolling the border."

ABC News' Luis Martinez contributed to this report.