The US and Mexico have reached an agreement to jointly develop drilling operations in the Gulf of Mexico.

The deal opens up some 1.5 million acres along the US Outer Continental Shelf, which runs east from the US Mexico border to 200 miles south of the Mississippi River.

US interior secretary Ken Salazar said the agreement will help the government to responsibly expand its domestic energy development. "US companies can now move forward with legal certainty, which has been missing in this area," he said.

US companies will now have the option to partner with Mexico’s national oil company Petroleos Mexicanos (Pemex) in drilling, under the terms of the new agreement. If the nations cannot agree on exploitation deals, they can take their share unilaterally.

The deal allows more cooperation to develop uniform safety guidelines for offshore energy development to avoid spills, which could affect both nations. This is in line with a previous agreement reached between US President Barack Obama and Mexican president Felipe Calderon in 2010.

It will also remove a moratorium on waters in a buffer area known as the Western Gap. The area was put off-limits by both the nations in the year 2000.

The Deepwater Horizon oil spill in 2010 led to the extension of the moratorium through to 2014.