The suspense over the new Karnataka chief minister intensified on Monday as state Congress president D K Shivakumar cancelled his visit to the national capital citing health issues after he and Siddaramaiah, both frontrunners for the top post, were called by the central leadership for discussions.

The three central observers, who interacted with party MLAs on their choice for the CM's post after the Congress Legislature Party meeting on Sunday, briefed party chief Mallikarjun Kharge and submitted their report.

After the meeting, Randeep Surjewala, AICC in-charge for Karnataka, said that the party was not in a hurry and would take a decision after wider consultations with state leaders.

"The observers have submitted the report to the Congress president. We will hold consultations with all senior state leaders, including Siddaramaiah and Shivakumar, and after that a decision will be taken by the Congress president," he told reporters outside Kharge's residence after the meeting.

"The Congress president believes that the decision should be taken while keeping unity, unanimity, consensus and welfare of Kannadigas in mind," he told PTI.

Sources said the party is likely to take a decision in the next two-three days.

Former chief minister Siddaramaiah and Shivakumar were called by the party high command for further discussion on government formation. Siddaramaiah arrived this afternoon in the national capital but Shivakumar cancelled his visit, hours after confirming he would be flying to Delhi, fuelling speculation that the factional fighting in Karnataka Congress had reared its head again.

Shivakumar cited health reasons for the change in his travel plans.

"I have some problem in the stomach. Doctor is coming in 10 minutes. It's burning. It looks like some infection and I have a fever..... please let me be free...," he told reporters.

Late Monday night, Shivakumar's brother and Congress MP D K Suresh met party president Kharge at the latter's residence in Delhi and thereafter told reporters that the state party chief will be visiting Delhi on Tuesday.

"Yes, he will be coming tomorrow," D K Suresh said in response to a question from reporters.

Amid various claims about the number of MLAs supporting him and Siddaramaiah for the CM's post, Shivakumar said earlier on Monday that his strength is 135, as under his presidency in the state the party had won the seats.

The move by Shivakumar, seen by many as a "pressure tactic" to assert his claim on the top post, indicated that the leadership war in the southern state is far from over.

Party sources, however, said it will not be "blackmailed" by anyone and that all MLAs belong to the Congress and not any individual.

The three observers deputed by the Congress - Sushilkumar Shinde, Jitendra Singh and Deepak Babaria - returned to the national capital on Monday morning.

They, along with AICC general secretary in-charge of Karnataka and general secretary organisation K C Venugopal, met Kharge and held discussions on the views expressed by the MLAs, the sources said.

The deliberations in Delhi were preceded by intensive consultations, one-on-one interaction with MLAs and even a 'secret ballot' in Bengaluru during and after the meeting of the Congress Legislature Party.

After the Congress party's stupendous victory in the May 10 assembly polls, the party faces the uphill task of satisfying the two camps and is working on a 'formula'.

The CLP had on Sunday passed a resolution authorising party president Mallikarjun Kharge to decide on the chief ministerial nominee. Both Siddaramaiah and Shivakumar have never hid their CM ambitions Earlier in the day, Shivakumar said that he has been called by the central leadership.

"Since today is my birthday, a lot of people have come to wish me. I have to go to my deity with my family, after going there, I will leave for Delhi. I don't know what time I will be going to Delhi. I will take whichever flight is available," he had said.

Senior party leader B K Hariprasad said the MLAs were asked for their open feedback on their choice of chief minister during their interaction with the observers and also a secret ballot was held for the CM's name. The observers have brought the ballot boxes to Delhi along with them.

Kharge is likely to take a decision on who will be the next chief minister of Karnataka soon. He is also likely to hold consultations with top Congress leadership, including Sonia Gandhi and Rahul Gandhi, before arriving at a decision.

Meanwhile, the party is also gearing up for preparations for making the swearing-in ceremony of the chief minister a big show of strength, where several opposition leaders will be invited.

Supporters of both Siddaramaiah and Shivakumar had raised slogans projecting them as the next chief minister outside the meeting of the Congress Legislature Party on Sunday evening.

A poster war by supporters of both leaders also erupted soon after the party won the election.

While Siddaramaiah is a leader with mass appeal, is popular among all sections and has the experience of running a government of a full five-year term from 2013-18, Shivakumar has strong organisational capabilities, is considered resourceful and Congress' troubleshooter during tough times and has the backing of the dominant Vokkaliga community, its influential seers and leaders.

Congress MP Naseer Hussain told reporters that both Siddaramaiah and Shivakumar are senior Congress leaders and have fought together against the BJP.

"Both led this fight from the front, both did their best to strengthen the party. Both have contributed to the victory of the Congress, but only one can become the Karnataka chief minister. Let us see what is the opinion of the members of the CLP," he told reporters outside Kharge's residence.