Often seen as a possible opposition candidate for prime ministership in 2019 Lok Sabha polls, he said no serious attempt is currently being made to bring together non-BJP parties.
A grand alliance of the opposition parties at the national level is certain to win the elections but no such scene was in sight, he said.
He asserted there is no problem in the ruling grand alliance in Bihar and mocked speculation about his growing proximity with BJP, saying he would not offer denial on all kinds of reports as denial is 50 per cent confirmation.
Kumar's strong support to 'notebandi', which has riled leaders like TMC chief Mamata Banerjee, came at a meeting organised by his party JD(U) and later at HT Leadership Summit even as another top leader of his party Sharad Yadav targeted the Modi government over demonetisation in his presence.
"This 'notebandi' is a positive step which will lead to benefits. It will happen," the JD(U) President said, terming corruption and black money as a "big sin and festering wound" which must be eradicated.
"Severe steps will have to be taken. That is why we offered our support to this (demonetization). It is a positive beginning... Whenever there is an attack on corruption, I will support it," he said.
The JD(U) president also refrained from any criticism on the manner of its implementation causing inconvenience to people, an issue vociferously raised by the opposition and his party colleague Yadav.
Asked about Yadav and other opposition parties raising the issue of people's difficulties, he said, "I don't speak about it because those facing difficulties should be speaking.
No such voice is being heard. People are in difficulty but the poor thinks he is facing problem today but a lot of money of the rich is sinking."
Yadav is highlighting these difficulties, Kumar said, adding that there is no problem in that. "We have no difference of opinion."