Pakistan Tehreek-i-Insaf chief Imran Khan and cleric Tahirul Qadri are protesting alleged vote rigging in polls last year and demanding Sharif's resignation and holding of fresh polls.
Khan and Qadri had separately launched protests from eastern city of Lahore on August 14 to dislodge the 15-month-old government and have been camping in the capital since last Saturday with thousands of their supporters.
The political crisis has paralysed the government and raised questions about Pakistan's democratic stability.
With an aim to end the protests, government officials yesterday met with senior members of Khan's Pakistan Tehreek-e-Insaf (PTI) party. The protest leaders had previously rebuffed offers of negotiations from Sharif's Pakistan Muslim League-N.
The latest round of talks came at a time when lawmakers from Khan's party have resigned from the National Assembly and the Speaker is yet to accept them.
The government enjoys a majority with ruling PML-N having 190 members in a House of 342. Khan's PTI is the third largest party in the National Assembly.
At the end of second round of talks, the two sides told media that they will meet again today.
PTI vice chairman Shah Mehmood Qureshi told reporters the next round of talks would be held later in the day.
A government delegation also met Qadri's team yesterday to discuss the demands of the cleric's Pakistan Awami Tehreek (PAT) movement, but the PAT came away dissatisfied.
Their talks were dominated by the issue of the alleged murder of at least 10 PAT workers in clashes with police in Lahore in June, for which Qadri wants arrests made and a legal case launched.
The fragile dialogue between the government and protesters has raised hopes of resolution of the political crisis.
Sharif has invited former president and PPP leader Asif Ali Zardari for a luncheon meeting today to discuss issues related to the political impasse.