Capping weeks of intensified efforts, decks were on Thursday cleared for the merger of B S Yeddyurappa-led Karnataka Janata Paksha with BJP, as both parties jointly announced their union declaring that they would complete all the formalities within three or four days.

The much-expected merger announcement by Yeddyurappa came after a delegation of Karnataka BJP leaders met and formally invited him back to the party fold, thus setting the stage for the two parties to come together.

"We have decided to merge KJP with BJP," said Yeddyurappa, flanked by BJP national General Secretary Ananth Kumar, who was perceived to be his bitter rival, and his other senior colleagues including state unit President Prahlad Joshi.

Sources in BJP's central leadership said his return to the party fold is unconditional and he will not contest the coming Lok Sabha elections.

BJP extended the formal invitation to Yeddyurappa soon after it held the party's core committee meeting and proceeded to his house to welcome him back to the party, which he had deserted over a year ago and formed KJP.

Losing no time in accepting the invitation, Yeddyurappa announced the merger decision, saying, "All formalities will be completed within three or four days. From this minute, we both are going to work for winning more than 20 (of the 28) Lok Sabha seats in the state."

Ananth Kumar said with Yeddyurappa's decision, BJP's strength would increase "10 fold" and added that "good news" had been conveyed to party President Rajnath Singh who gave his "good wishes".

The merger moves had gathered steam in recent weeks, with Yeddyurappa giving clear indications that it was only a matter of time before his return to BJP whose state leaders also got the green signal from the party top brass.

After the core committee meeting, Joshi said, "There is absolute consensus (about the entry of Yeddyurappa). There is no problem. Unanimously the state unit has decided that we have to fight (Lok Sabha) election together."

Joshi said Yeddyurappa has decided to merge his party with BJP and "this information has been duly conveyed" to the national president of the BJP.

"I whole-heartedly welcome Yeddyurappa to BJP, and together, from tomorrow itself we will travel the entire state and rebuild the confidence among the workers of both the parties," he said.

"All the formalities, as far as merger is concerned, both technically and legally, whatever is needed to be done, will be done at the earliest," he said.

The two parties had put the merger efforts on top gear in recent weeks, having learnt a bitter electoral lesson in the May 8 Assembly polls, in which KJP had played a spoiler to BJP, causing the collapse of its first ever government in the South.

KJP had garnered six seats and 10 per cent vote share in the Assembly polls but had failed make a big impact as an independent force, creating an uncertain future for the party.

"From this moment, we will forget the past..." said Yeddyurappa, who had snapped his more than four decades old association with BJP in December 2012 nursing bitterness against central leadership for removing him as chief minister.

Indicted by Lokayukta on illegal mining issue, a reluctant Yeddyurappa was asked to vacate his chair in July 2011, after which Sadananda Gowda succeeded him but made way to Jagadish Shettar, both of whom were made to spend sleepless nights by the Lingayat strongman before floating KJP.

Yeddyurappa had written to NDA Chairman L K Advani conveying KJP's willingness to be part of the BJP-led combine but had received no response from the BJP veteran, who was reported to be not so enthusiastic about him.

"All people are expecting Narendra Modi to be Prime Minister, for that we are going to work day and night from today onwards," Yeddyurappa said.

Ananth Kumar said Yeddyurappa has taken a "good decision" and it was a "historic day" in state politics, as he praised the latter for being one of the builders of BJP.

He said the decision had been taken in the presence of BJP leaders Joshi, Shettar and former Deputy Chief Minister K S Eshwarappa and C M Udasi and Shobha Karandlaje, trusted lieutenant of Yeddyurappa, from the KJP.

Ananth Kumar said the "sole purpose" of the merger was to make India "free of Congress" as also the state and win 272 plus Lok Sabha seats.