Top opposition leaders are likely to attend the lunch meet hosted by Gandhi in the Parliament House library on a day that also marks the third anniversary of the National Democratic Alliance (NDA) government at the Centre.
Bihar Chief Minister Nitish Kumar, however, will not be there because of a prior engagement, sources said, adding that his party, the JD-U, would be represented by Sharad Yadav.
The sources also said the Congress had not invited Delhi chief minister and AAP leader Arvind Kejriwal.
The leaders would explore the possibility of fielding a joint candidate for the upcoming presidential election.
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Sources said West Bengal Chief Minister Mamata Banerjee, RJD supremo Lalu Prasad, CPI-M's Sitaram Yechury, CPI's D Raja and JD(U) veteran Yadav, who is himself a possible contender for the top constitutional post, would attend the lunch.
Invitations had been sent to JD(U), CPI, CPI-M, SP, DMK, NCP, RJD and TMC, besides some other big and small regional parties.
Efforts are on to bring arch political rivals in Uttar Pradesh -- the Samajwadi Party and the Bahujan Samaj Party-- together on a common opposition platform ahead of the presidential poll.
Several names have been doing the rounds as probable candidates. Among them are former West Bengal Governor and Mahatma Gandhi's grandson Gopal Krishna Gandhi, former JD(U) president Yadav, Former Lok Sabha speaker Meira Kumar and NCP chief Sharad Pawar. The NCP leader has, however, ruled himself out of the race.