An emergency joint session of parliament in Pakistan has been adjourned as PM Nawaz Sharif seeks to rally support, with protesters calling for his resignation.
It follows three days of violent clashes which left three people dead.
The army has denied suggestions it is backing anti-government groups, insisting it is "apolitical".
Sharif - who was elected last year - has said he is determined to protect democracy and will not resign.
Tuesday's emergency session of both houses of parliament could last several days and the prime minister will make an address after every representative has had a chance to speak.
Correspondents say the session is an attempt by the government to shore up its support.
Qadri is supported by another opposition politician, Imran Khan - who argues that the June 2013 elections were rigged.
The BBC's M Ilyas Khan in Islamabad says police were deployed in strength late on Monday as the government resumed negotiations with Qadri and Khan.
The prime minister - who was elected with an overwhelming mandate - has pledged "not to let the people's mandate be hijacked by intimidation".
His Pakistan Muslim League is the largest political party in the country.
The country's national PTV television channel on Monday was briefly taken off air after protesters stormed its headquarters in Islamabad.
The army's public relations wing on the same day issued a statement in which it described itself as an "apolitical institution" that "categorically rejected" supporting either Khan or Qadri.
The army's intervention came after a senior figure in Khan's PTI party, Javed Hashmi, claimed Khan had told senior party members that the army and intelligence services were ready to help him and Qadri topple the government.
Our correspondent says that a form of anarchy reigns on Islamabad's high-security Constitution Avenue, where crowds have been gathered for nearly three weeks.
A popularly elected government, which now also has the support of almost all opposition forces, is being cornered by a minority political group and the followers of a cleric who runs a charity network, our correspondent says.
On Monday, thousands of demonstrators - some wielding batons and throwing stones - moved on the main building housing Pakistan's federal bureaucracy and Prime Minister's House. A number of riot policemen were reported to have been injured.
Protests had been peaceful until Saturday, when violence broke out. Three people died and hundreds were injured.
Last year's elections marked Pakistan's first civilian transfer of power. Sharif won by a landslide and BBC correspondents say the vote was deemed to have been generally fair.