The Union Cabinet will meet in New Delhi on Tuesday evening to decide on imposing President's rule in Karnataka.
Karnataka Governor Rameshwar Thakur on Monday recommended Presidents' rule in the state after the H D Kumaraswamy government was reduced to minority following the withdrawal of support by the BJP.
Analysis: BJP acted in haste, JD-S too late
The Congress core group met on Monday night to take stock of the political situation in the state hours after Chief Minister Kumaraswamy submitted his resignation to the governor.
The meeting, held at the residence of Prime Minister Manmohan Singh, was also attended by Congress president Sonia Gandhi, senior ministers Pranab Mukherjee, Arjun Singh, A K Antony and H R Bharadwaj, National Security Adviser M K Narayanan and Home Secretary Madhukar Gupta.