"We appeal to all other opposition parties to support us," Congress President said.
Talking about Nitish Kumar, Lalu Prasad Yadav said-"Nitishji called me, said that it is his personal decision. I would appeal to him to rethink. Won't break the alliance."
"Will meet him (Nitish Kumar) tomorrow. Ask him to think, should not do a historical mistake, your decision is wrong," Lalu added.
Hectic parleys between leaders of non-NDA parties began on Thursday morning, hours ahead of a crucial opposition meeting.
After the JD-U's decision to support NDA presidential nominee Ram Nath Kovind, the Congress stepped up efforts to keep the opposition united as its top brass held discussions with the leaders of a host of other parties.
Cracks appeared in the opposition camp after the JD-U's surprise decision yesterday, as its chief Nitish Kumar was the one who had initiated the process for a joint opposition strategy on the issue.
Sources said a contest for the country's top constitutional post is on the cards as the majority in the opposition sees it an "ideological battle" that has to fight.
"No matter what happens, we will contest the election," a senior left leader said.
By naming Kovind, a Dalit, the NDA has put the opposition camp in a fix as it has now been forced to think of a suitable Dalit candidate to oppose Kovind so as not to be branded "anti-Dalit" by the ruling dispensation.
(With inputs from agencies)