Another round of discussion between the SLFP and the SLPP will take place tomorrow.
The discussion follows a one-on-one meeting between President Maithripala Sirisena and Opposition Leader Mahinda Rajapaksa last week.
The talks are aimed at forming an alliance before the next Presidential election.
SLPP sources said President Sirisena had agreed "in principle" to support SLPP Presidential candidate Gotabhaya Rajapaksa.
However, the arrangement within which the two parties will function as coalition partners will be further discussed, party sources added.