"The Congress party has extended its support and we have accepted it," Danish said.
"JD(S) had always maintained that HD Kumaraswamy will be CM. As per results, we're doing everything to keep BJP out of power," he added.
Danish said both the JD(S) and the Congress will jointly go to meet Governor after 5.30 pm today.
After the initial euphoria of the Bharatiya Janata Party crossing the half-way mark in the 224-member Assembly where two constituencies didn't vote on Saturday, Election Commission data showed the BJP could end up with 104 seats.
This would be eight seats short of a simple majority in a House where no one else appeared ready to back the BJP.
The Congress, despite being bruised in an election it had hoped to win, was set to take 77 seats and the JD-S could be victorious in 38 constituencies -- two short of its tally of 2013.
Independents and smaller parties would bag three seats.
As it became clear that the BJP might not cross the half-way mark, Congress leaders quickly got in touch with the JD-S of former Prime Minister H.D. Deve Gowda and his son and former Chief Minister H.D. Kumaraswamy.
Congress General Secretary Ghulam Nabi Azad told the media in the company of outgoing Chief Minister Siddaramaiah that the JD-S had accepted the Congress offer of support.
"We will meet the Governor and stake claim (to form a government)," he said. "Our numbers put together will be more than the BJP's."
Informed sources said the JD-S could get the Chief Minister's post in the event of a tie-up with the Congress.
But the BJP remained confident of taking power again in Karnataka. "We are confident of winning," spokesman S. Shantharam told IANS.
The claim was echoed by other BJP leaders both in Bengaluru and New Delhi, where its Chief Ministerial candidate B.S. Yeddyurappa, who won from Shikaripura, was set to meet BJP President Amit Shah later on Tuesday.