Pakistan's top nuclear scientist has confessed to leaking nuclear secrets to Iran, Libya and North Korea.
Khan (l) meeting General Musharraf
Abdul Qadeer Khan met President Pervez Musharraf on Wednesday and later went on TV to accept full responsibility for all nuclear transfers.
Dr Khan, regarded as a national hero, told the nation he had acted without authorisation and begged forgiveness.
President Musharraf said the case, which has sparked a national outcry, had traumatised Pakistan.
The cabinet will meet on Thursday to discuss what action to take.
Pakistan began an inquiry into possible illegal transfers late last year after the UN passed on information it had gathered about Iran and Libya's nuclear programmes.
A government statement issued on Wednesday read: "Dr AQ Khan submitted before the president that he
accepts full responsibility for all the proliferation activities.
"Dr Khan has submitted his mercy petition to the president and requested clemency in view of his services to national security."
Later Dr Khan made his own televised statement in which he cleared President Musharraf and other government and military officials of any involvement in nuclear proliferation.
"There was never ever any kind of authorisation for these activities by the government. I take full responsibility for my actions and seek your pardon," Dr Khan said.
He told his television audience: "I have chosen to appear before you to offer my deepest regrets and unqualified apologies."
On Saturday, Dr Khan was sacked as special science and technology adviser to the president.
Then on Sunday officials said he had signed a confession admitting he had traded nuclear technology information to other countries.
Later on Wednesday, President Musharraf chaired a meeting of the top nuclear decision-making authority to discuss Dr Khan's plea for mercy.
The National Command Authority decided to refer a decision to Thursday's cabinet meeting.
More than 15 people from the nuclear enrichment facility that Dr Khan used to run, Khan Research Laboratories (KRL), have been questioned in the nuclear transfers investigation.
Khan is widely seen in Pakistan as a hero for his nuclear work
Relatives of some of those still detained insist on their innocence.
Mohammed Shafiq, whose father was director-general of maintenance and construction at KRL, said: "Khan was forced to make this statement. We don't know if it's true or not. My dad said he was innocent. The team members at KRL have never dealt with Iran or Libya."
A leading Islamic party said a national protest planned for Friday would go ahead despite the apology.
Shahid Shamsi, spokesman for Jamaat-e-Islami, said: "The government has insulted Abdul Qadeer Khan by forcing him to read out a statement on state television."
He said evidence against the scientists should be presented before parliament or in court.
Pakistani officials say Dr Khan ran a network that systematically smuggled nuclear equipment to third countries using chartered planes.
They say the network shared secret designs for centrifuges capable of producing weapons-grade uranium.
Dr Khan, it is alleged, also secretly travelled abroad to explain to Iranian, Libyan and North Korean scientists how to make nuclear bombs.
However, he remains popular in Pakistan and his dismissal on Saturday sparked a national outcry.
Correspondents say the government has to decide whether to prosecute Dr Khan, a move that could provoke a domestic backlash.
Opposition parties accuse President Musharraf of bowing to American pressure over the move.
On Wednesday, the White House welcomed Pakistan's attempts to crack down on nuclear proliferation but spokesman Scott McClellan said it was up to Islamabad to decide on any prosecutions.