"Whenever there is talk of secularism or a secular state, Congress is with it. It's the duty of secular forces to assist each other," Shinde told reporters here.
"Casteism and communal forces cannot run the country ... only secular institutions can run the nation," he said in a veiled attack on the BJP.
"When I was MP, he (Nitish) was Railway minister," Shinde said describing the Chief Minister as "a good human being and known to me from the past."
The Chief Minister was present in the airport at the time Shinde spoke, but they were not together.
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Ever since four Congress MLAs voted in favour of Nitish Kumar during the June 19 trust vote, speculation is rife about a future relationship between the Congress and JD(U).
Congress has ended its ties with long time friend Lalu Prasad's RJD in Bihar and is contesting all elections on its own in the state since the 2009 Parliamentary polls, at the insistence of its Vice-President Rahul Gandhi.