US President Barack Obama has signed into law a $600m (£385m) bill providing increased security along the US-Mexico border.
The US Senate had reconvened on Thursday during its August recess to pass the measure.
The funds will mostly be directed to activities on the south-west border, such as hiring 1,000 border patrol agents.
Money will also pay for surveillance technology, including unmanned drones.
A further 250 immigration and customs enforcement agents will also be funded by the bill.
"This new law will also strengthen our partnership with Mexico in targeting the gangs and criminal organisations that operate on both sides of our shared border," Mr Obama said in a statement after the bill passed on Thursday.
Homeland Security Secretary Janet Napolitano told reporters that it would take eight months for the new border patrol agents to be recruited, trained and deployed to the border.
She also said that border crossings into the US were down 50% as a result of extra security and a weakened economy with fewer jobs for migrants.
Republicans and Democrats agreed to pass the bill on Thursday by a "voice vote", requiring only two senators to be present.
Senator Ben Cardin, Democrat of Maryland, presided while Senator Chuck Schumer, Democrat of New York, voted in the 40-minute session.
Mr Schumer, the measure's chief sponsor, hopes it will pave the way for comprehensive immigration legislation to be considered after the August recess.
"Both moderate Democrats and Republicans said they wouldn't even consider comprehensive reform until we did something about the border," Mr Schumer said.
Some Republicans appear unsatisfied though, with Senator Jeff Sessions calling the bill "a small measure" which "if it is not followed by strong, sustained action, it is yet another gesture without consequence".
The $600m will be paid for by raising fees on some foreign work visas.
Thursday's session was only the second time in four decades that the Senate has been called back into session during August. The other time was to pass emergency measures related to Hurricane Katrina in 2005.