The top commander of American and NATO forces in Afghanistan is expected to visit Pakistan amid heightened tensions over militant networks allegedly based on Pakistani soil and still-closed military supply lines.

The Pakistani military said U.S. Marine Gen. John Allen's Wednesday visit would focus on border cooperation.

Relations between the U.S. and Pakistan have plunged recently.

The U.S. is frustrated with what it says is a failure by Pakistan to go after the Haqqani network, a militant group that has attacked American forces across the border. The U.S. and Pakistan have been at loggerheads over Pakistan's closure of supply lines to Afghanistan.

The lines were closed after U.S. airstrikes accidentally killed 24 Pakistani border troops.