WASHINGTON -- With time running out on Congress before a long recess, Sen. Claire McCaskill and Democrats offered a $600 million plan today to bolster security along the U.S.-Mexico border.

McCaskill and Sen. Charles Schumer, D-NY., said at the Capitol that they want to raise fees on foreign corporations importing low-skill workers to pay for hiring 1,500 additional border patrol agents and bringing in unmanned drones for monitoring.

"The bill is our answer to the problem in Arizona. The bill will do what we should be doing in this country -- enforce our borders," said McCaskill, D-Mo.

Schumer said Democrats hope to corral Republicans for a unanimous vote to bring up the immigration proposal before adjourning later today.

But the immediate future of the proposal seemed in doubt given the late hour and the dearth of bipartisanship in Congress at the moment.

The last-ditch effort raised questions about the Democratic intentions and whether they're playing politics.

McCaskill noted that the plan could still get a vote after Congress returns in September. "What's political about this is to posture and do nothing," she said.

McCaskill has voted for GOP-sponsored border plans and thus far has declined to support her party's broader immigration proposals.

Before she endorses Democratic-drawn comprehensive legislation, "We've got to demonstrate to the American people that we can control the border and enforce the law," she said in an interview, referring to employers who hire illegals.