Mr Zardari benefited from the 2007 corruption amnesty deal
President Asif Ali Zardari has handed control of Pakistan's nuclear arsenal to his prime minister, in an apparent bid to ease political pressure.
The move was a "giant leap" forward that empowered the PM and parliament, Mr Zardari's spokesman said.
But analysts said it was an attempt to placate political and military critics, as an amnesty protecting Mr Zardari from possible prosecution expired.
The amnesty gave him and several others immunity from corruption charges.
The presidency announced that control of the National Command Authority, responsible for nuclear weapons, had shifted to Prime Minister Yousuf Raza Gilani.
"The president has handed over his power regarding the national command and control authority to me and has issued an ordinance," Mr Gilani was quoted by news agency AFP as saying.
Thousands of politicians, lawyers and bureaucrats are said to have benefited from the amnesty, known as the National Reconciliation Ordinance (NRO).
It was introduced by former military ruler Pervez Musharraf in 2007 as part of a proposed power-sharing plan with Mr Zardari's late wife, Benazir Bhutto.
But the amnesty was challenged in the Supreme Court, which told Mr Zardari to get approval of all decrees issued by Mr Musharraf by 28 November - something he has been unable to do.
Correspondents say the expiration of the amnesty threatens political turmoil at a time when Pakistan is battling Taliban and other militants along its border with Afghanistan.
The opposition wants lawmakers covered by the NRO to step down.
And while Mr Zardari has additional immunity from prosecution as president, his opponents want the Supreme Court to declare his election illegal.
Mr Zardari is currently very unpopular and observers say devolving more power to parliament could be a way of bolstering support.
Presidential spokesman Farhatullah Babar said the transfer of the National Command Authority was "a giant leap forward to empower the elected parliament and the prime minister".
Mr Zardari was "giving up the dictatorial powers that Gen Musharraf - as an unelected leader - needed to keep himself in power", another spokeswoman said.
But critics dismissed the move as "window-dressing". Rasool Bakhsh Rais, a political science professor at Lahore University of Management Science, told the Associated Press news agency that it was a "survival strategy" to retain his position.