The joint session of the Senate and National Assembly, summoned by President Asif Ali Zardari, will debate the recommendations of the Parliamentary Committee on National Security for revamping the country`s strategic ties with the US.
The unprecedented parliamentary review of bilateral relations was ordered by Prime Minister Yousuf Raza Gilani after 24 Pakistani soldiers were killed in a cross-border NATO air strike in November.
Even before that, Pakistan-US ties were buffeted by a string of crises last year, including the gunning down of two Pakistani men by a CIA contractor in Lahore and the killing of al-Qaeda chief Osama bin Laden by US special forces in the garrison town of Abbottabad.
Shortly after the joint session began, Parliamentary Committee on National Security head Raza Rabbani briefed the lawmakers on the work done by the panel in framing the recommendations for revisiting ties with the US.
The outcome of the joint session, expected to continue for three days, has been awaited anxiously by the US because of its potential fallout on the US-led war on terrorism and Washington`s plans to pull out its troops in Afghanistan by 2014.
US-Pakistan ties have virtually been on hold since the NATO air strike and Islamabad has turned down requests for visits by top American officials like Special Representative for Afghanistan and Pakistan Marc Grossman.
The US described the NATO attack as unintentional but this stand has been rejected by the Pakistani military.
Pakistan`s top civil and military leadership have held two meetings in the run-up to the joint session of Parliament to review and fine-tune the 35 or so recommendations made by the Parliamentary Committee on National Security for revamping bilateral relations.
The issue has also been reviewed separately by the military top brass, which plays a key role in shaping foreign policy, particularly relations with the US and India.
The influential Dawn newspaper said in a report today that the joint session was unique.
"Foreign policy debates in parliament in the past may have influenced government decisions, but the one beginning on Tuesday will be the first institutionalised effort of its kind for a parliamentary guidance in foreign relations," the report said.
The newspaper quoted parliamentary sources as saying that the recommendations of the joint sitting "would not be the final word and would serve only as a guideline for the government in negotiating arrangements with the US so long as the Afghan conflict continues".
The Pakistan People`s Party-led government, which took office in March 2008, has by and large followed arrangements made during the regime of military ruler Pervez Musharraf for ties with the US, especially for the war on terrorism.
However, opposition political parties have called for a review of Pakistan-US ties, because of public anger over US drone strikes in the country`s tribal areas, the US raid against bin Laden and the NATO air strike in November.
Following the air strike, Pakistan shut down NATO supply routes and forced the US to vacate Shamsi airbase, believed to have been a hub for CIA-operated drones.