His comments a day after the JD(U) demanded that Mr Kumar be projected as the BJP-led NDA's face in Bihar.
In Delhi for an official event, the Bihar BJP leader said he did not see any contradiction in the JD(U)'s stand as Mr Kumar, as the chief minister, had been the NDA's leader earlier as well when he was a BJP ally.
"Narendra Modi is the country's prime minister while Nitish Kumar is the leader in Bihar. So the votes we will get in Bihar will be in Narendra Modi's name and in the name of Kumar's works. I don't see any contradiction here. Kumar is the face in Bihar while Narendra Modi is the prime ministerial face in the country," he told reporters.
He, however, parried query on division of 40 Lok Sabha seats in the state among the four NDA parties, which include Ram Vilas Paswan-led LJP, Upendra Kushwaha-led RLSP besides the JD(U) and BJP.
He said the seat-sharing will be decided at an opportune time.
The Bihar deputy chief minister, however, asserted that division of seats will be a smooth affairs, saying "When hearts have met, then seats are not a big issue".
The JD(U) was the senior partner in Bihar till 2013 when it walked out of the BJP-led NDA. It had contested 25 seats in the 2009 polls while the BJP fought on 15.
However, the BJP had swept the 2014 polls, winning 22 seats while its allies LJP and RLSP won six and three seats respectively. The JD(U) won only two, when it was not part of the NDA alliance.
Recent statements from JD(U) leaders are being seen as an attempt by the party to ensure that the BJP does not dictate terms during the seat-sharing talks.
Sushil Modi asserted that the NDA will win all 40 seats in Bihar in 2019, saying the opposition RJD-Congress alliance has weakened after Mr Kumar left it to join the NDA and 70 per cent voters are with the ruling alliance.