A presidential election will need to be held before July 25, the day when President Pranab Mukherjee's term expires.
"Pawar ji met Sonia Gandhi. We are working towards a grand alliance for the presidential election," NCP leader Tariq Anwar told IANS.
"The talks are going on not only for a grand alliance for presidential elections but also for the 2019 Lok Sabha polls," he added.
Mr Pawar's meeting with Sonia Gandhi took place a day after senior Janata Dal-United leader Sharad Yadav also met her on the issue.
The opposition parties led by the Congress are trying to forge an alliance of like-minded parties to put up a joint fight to the ruling National Democratic Alliance in the presidential election and to carry it till 2019 general elections.
Sonia Gandhi had earlier met Bihar Chief Minister Nitish Kumar, Communist Party of India-Marxist General Secretary Sitaram Yechury and CPI's D Raja to discuss the presidential election and the need to field a joint opposition candidate.
Earlier, BJP ally Shiv Sena had said that Mr Pawar is a "worthy leader and has the right credentials" tp become India's next President.
Sharad Pawar, 76, has served as Union Defence Minister under the PV Narasimha Rao government and Union Agriculture Minister between 2004 and 2014. He is also former Chief Minister of Maharashtra. He received the country's second highest civilian honour, the Padma Vibhushan, in 2017.