Khan, however, said he would abide by the Supreme Court's verdict on the issue of alleged rigging in last year's general elections. Both Khan and Qadri have been called by the court tomorrow in connection with the hearing on the protest, currently outside the Parliament.
Threatening to storm the Prime Minister's residence, the cricketer-turned-politician and Pakistan Tehreek-i-Insaf (PTI) chief refused to negotiate with the government until Prime Minister Sharif resigns. He told the media that he would abide by whatever the Supreme Court says.
In the first sign of thaw between the government and the protesters, Sharif today sent a four-member team to negotiate a deal with Pakistan Awami Tehreek (PAT) leader Qadri.
The move came after the powerful army called for calm following the breach by protesters of the high-security Red Zone that houses important government buildings including the Parliament House, Prime Minister House, President House, the Supreme Court besides the embassies.
"Situation requires patience, wisdom and sagacity from all stakeholders to resolve prevailing impasse through meaningful dialogue in larger national and public interest," military spokesman Maj Gen Asim Saleem Bajwa tweeted.
Qadri declined to give any guarantee about the success of the dialogue but maintained that he had never opposed talks.
The team sent to Qadri comprised of Minister for Frontier Region Qadri Baloch, Minister for Railway Saad Rafique, opposition leaders Ijazul Haq and Haidar Abbas Rizvi.
"Our leader had said that the negotiations should reach a conclusion which is in the best interests of the people," PAT representative Khurram Nawaz Gandapur told reporters after the delegation met Qadri in his bullet-proof mobile container.
"We are yet to put forward our demands and they would be presented once the government delegation visits us again. I am hopeful of a positive result to arise out of our efforts," he said.
Khan was quoted by Dawn News as saying that Sharif is "Pakistan's Hosni Mubarak" and alleged that he had killed innocent people in Lahore's Model Town, in an apparent reference to the killing of 14 Qadri supporters in June.
Khan called for those involved in rigging last year's polls to be brought to the book.
Khan maintained his aggressive stance today, tweeting, "Tonite we will celebrate Azadi at D Chowk (inside the Red Zone)."
"I want all Pakistanis 2 get here breaking all barriers. Warning police 2 release r ppl or v will punish them 4 unlawfully detaining r ppl," Khan said.
PTI leader Shah Mehmood Qureshi said, "We have decided not to immediately enter negotiations with the government".
"The party decided that the foremost fundamental condition is that the Prime Minister step down, and that no dialogue can be initiated unless the resignation takes place," he said.
Earlier, Qureshi had said that the party is willing to sit at the negotiating table with the government.
Talks with Qadri began, after Prime Minister Sharif's brother Shahbaz once again met army chief Gen Raheel Sharif in the garrison city of Rawalpindi, Geo TV reported.
Analysts believe after several crucial behind the scenes meetings it is expected the standoff between the government and protesters might end.
But the two sides still have a long way to go as Khan has so far spurned all effort for talks.
Also, Qadri is a hard bargainer and may demand a hefty price before backing off, analysts said.
Earlier, Qadri asked his supporters to end the blockade of the Parliament and allow legislators to move out of the building.
Under pressure from the call by protesters to storm his residence, Prime Minister Sharif today decided to meet Khan in an effort to end the anti-government protests.
"It has been decided PM (Sharif) will meet Imran Khan for the sake of country," Minister for Railways Khawaja Saad Rafique, a close aide of Prime Minister Sharif, tweeted. Rafique did not give the time for meeting.
As the drama in the capital unfolded, the session of Pakistan's lower house of parliament, attended by Sharif, was held.
The military has said the buildings in the red Zone are symbols of state and being protected by army, so the sanctity of these national symbols must be respected.
Khan and Qadri have both alleged rigging in the polls last year and called for a re-election. In the elections, Sharif's PML-N had won 190 out of 342 seats. Khan's PTI got 34 seats, the third largest bloc in the legislature.
"If Nawaz Sharif does not resign then we will enter into the PM House," Khan said while addressing thousands of anti-government protesters who entered the heavily fortified 'Red Zone' and set up camp in front of the Parliament House late last night.
Pakistan Army has taken charge of the Interior Ministry's control room, Dawn News reported.
The army, which has so far been passive in the confrontation between the government and protesters, has a history of capturing power from democratically elected governments.
In its 67-year history, Pakistan has witnessed three coups, including one against Sharif in 1999 by the then army chief General Parvez Musharraf.