Nato will once again be able to send lorries from Pakistan into Afghanistan to supply its forces.
Islamabad and Washington have agreed a deal to end a seven-month dispute after 24 Pakistani soldiers were killed by Nato aircraft last November.
Pakistan’s Prime Minister Raja Pervez Ashraf said the closure of the routes was damaging ties with the US and other coalition countries.
American Secretary of State Hillary Clinton stopped short of an outright apology for the deaths, but said she had offered “sincere condolences”.
The incident, close to the Afghan border, sparked a further rift between Washington and Islamabad.
Ties had already been strained by the US raid that killed Osama bin Laden.
Freeing up the lorries in Pakistan will also ease costs for Nato. Sending supplies into Afghanistan from the north costs two and a half times as much. The Pakistani routes will become even more important as more Nato troops are withdrawn.