Pakistani President Pervez Musharraf has accused the al-Qaeda network of trying to kill him last December.
Tribesmen are being urged to join the fight against militants
The president said a Libyan man had a role in both attempts on his life, and one of his associates was under arrest.
In a hard-hitting speech to tribal elders in Peshawar, he said there were 500-600 al-Qaeda members hiding in the South Waziristan semi-autonomous area.
Correspondents say his comments were the strongest yet about the presence of al-Qaeda in the mountainous region.
The BBC's Haroon Rashid in Peshawar says the president made a combative hour-long speech under tight security in Peshawar, the capital of North-West Frontier Province.
"The man who organised the suicide attacks against me was from Libya and a member of al-Qaeda," the president said, without naming the individual.
He said that the suspect had given about $30,000 to a Pakistani man who recruited Islamic militants to carry out the attacks.
The president said the government would release more details about the plot, and the suspects would soon be shown on television.
The president survived two assassination attempts only 10 days apart in December. On both occasions he was travelling in a motorcade.
He told the gathering of 500 tribal elders from all over Pakistan's western semi-autonomous tribal areas to help the government clear the area of unwelcome foreigners.
Our correspondent says the president suggested that tribesmen could give him more help in the battle against terrorism.
The president said so far government incentives for tribes people to hand suspects over had not been successful, even though the authorities had promised that they would not be extradited to another country.
He said that complete tribal support in the war against terrorism was necessary so that the country's image abroad could be improved.
"You give any name to them, al-Qaeda or not, but I say we will not allow these foreigners to stay in our tribal areas and create problems for us," he said.