Sensing defeat in the majority test in the assembly, Karnataka's newly elected Chief Minister B S Yeddyurappa of Bharatiya Janata Party today announced that he will resign from his post just a couple days after assuming office.

His decision came as because he lacked the required number in the assembly of the key southern Indian state.

B S Yeddyurappa said he is going to quit shortly before a motion he moved in the legislative assembly to ascertain majority was to have been put to vote.

The Supreme Court on Friday ordered a floor test in the Karnataka Assembly today, drastically cutting the 15-day timeline given by state Governor Vajubhai Vala to Yeddyurappa to prove his majority.

"I am going to resign as chief minister...I will go to Raj Bhavan (the Governor's office) and submit my resignation. "I will not face confidence vote...I am going to resign," Yeddyurappa told the assembly after a brief emotional speech while moving the motion.

His resignation will pave the way for the formation of a government led by regional party Janata Dal(Secular) state chief H D Kumaraswamy who has the backing of the Congress. The newly formed alliance has claimed the support of 117 MLAs in the 224-member House with an effective strength of 221.

BJP emerged as the biggest winner in the Karnataka state legislative assembly election held on May 12 but has fallen short of a majority in the 224-member House, sparking a scramble for power between the party and its arch rival Congress and Janata Dal (Secular).

The Congress party, which was voted out of power in last Saturday's election, tried to stop Yeddyurappa from taking the oath as chief minister by stitching up a last-minute post-poll coalition with Janata Dal (S), a smaller regional party.

But the BJP argued that it should get the first chance to form a government as it is the largest party and state governor Vajubhai Rudabhai Vala gave it 15 days to prove it has a majority, prompting the Congress to go to the Supreme Court.

Following a three-hour hearing that began around midnight, the Supreme Court on Thursday rejected the Congress claim that it already had a majority by joining hands with Janata Dal (Secular).

The BJP won 104 seats in the 224-member assembly, nine short of a majority. Congress bagged 78 seats and Janata Dal secured 37 seats. Together, Congress and Janata Dal (S) have 115 seats, two more than the majority mark.

Congress is desperate to cling on to Karnataka, its last major bastion after being defeated in 12 state elections since it lost the mandate to rule India to Modi in May 2014.

The BJP also desperately needed to capture power in Karnataka as it would have given the party a foothold in southern India, and a boost in the run-up to the national elections due early next year.