The Congress declared on Saturday night that it will not be joining Mulayam Singh Yadav's government in Uttar Pradesh "for the time being".
The decision was conveyed to Yadav and Samajwadi Party general secretary Amar Singh by Congress general secretary Nawal Kishore Sharma and Ahmed Patel, political secretary to party president Sonia Gandhi.
Ambika Soni, another Congress general secretary, said both Yadav and Amar Singh tried to contact Gandhi earlier in the day, but she was away on a tour of Rajasthan and Haryana.
The Congress decision comes two days before the vote of confidence that Yadav is seeking in the Uttar Pradesh assembly.
Last week, the Congress Working Committee had deliberated on the issue while empowering Gandhi to take a decision in the matter.
While the 16 Congress legislators in the state favour joining the government and were pressing the leadership to agree, a section of the central leadership is strongly opposed to any such move.
Earlier in the day, Gandhi remained non-committal whether her party would join Yadav's government. But in an informal discussion with reporters in Haryana, she insisted that the Congress support to the Samajwadi Party was the first step towards implementing the party's resolve after its Shimla conclave to start working with other secular parties to defeat communal forces.
PTI