Jameel Khan, a senior political official in the region, said the agreement was verbal and that negotiations with the tribesmen in Bajaur's Mamound border district had been going on for several months.
"Tribesmen led by elder Malik Abdul Aziz assured they would not shelter any foreign militants and would also not allow them to illegally cross the border," Khan said.
The agreement with the tribe in Bajaur, a mountainous region opposite the eastern Afghan province of Kunar, is the latest deal Pakistani authorities have struck in the hope of ending violence and cross-border attacks in the tribal belt along the country's border with Afghanistan.
Many al-Qaeda and Taliban members are said to have fled to Pakistan's semi-autonomous border lands, after US-led forces ousted the Taliban in 2001, where they are allegedly given shelter by Pashtun tribes.
Hundreds of people have been killed in clashes in recent years in Pakistan's attempts to clear out the foreign fighters and their allies. The recent deal was struck in the same district where a US air strike killed 18 people in January last year.
The authorities have struck two agreements in the Waziristan region, to the south of Bajaur, but US officials say the pacts have not stopped fighters crossing the border into Afghanistan and critics of the agreements say the pacts amount to giving the militants free rein.
Richard Boucher, the US assistant secretary of state for South and Central Asia, said the strategy was not working.
Earlier this week he told a news conference in Islamabad: "The political deal in Waziristan has not stopped the militancy. Unfortunately, it has not stopped the bombings against Pakistani civilians, it hasn't stopped the cross-border activity."
But Pervez Musharraf, the Pakistani president, has defended the pacts, saying they empower tribal elders and marginalise militants.
Shah Wali Kahn, a resident in the tribal areas, told Al Jazeera's reporter: "This tribal agency is peaceful and we want progress and prosperity. There is no terrorist element here. We want to send a message of peace to the world. Let the world come here and see the existing peace."