The eight-time MLA further claimed BJP would form a new government in the state by next week, drawing a strong reaction from state Congress chief Dinesh Gundu Rao, who hit out at him for making "illusionary statements" to 'confuse' people.
The claim by Katti came in the midst of public display of anger by some ministerial aspirants from Congress who were left out in the recent cabinet expansion.
Senior MLA Ramesh Jarkiholi, upset after being dropped from the H D Kumaraswamy ministry, has threatened to resign and said he would announce his future course of action later this week.
Chief Minister Kumaraswamy and senior Congress leaders and ministers have asserted that no MLA would resign and there was no threat to the stability of the six-month old government.
However, BJP state President B S Yeddyurappa separately said the party was not in touch with any disgruntled MLAs of Congress.
Speaking to reporters in Belagavi, Katti said: "Fifteen MLAs are in touch with me, I cannot divulge their names now, when time comes I will tell.
However, ruling out 'Operation Lotus' (engineering defections), Katti said, "we will welcome those who are pained in Congress and JD(S) and want to join our party. If they come, we will induct them into our party and form the government, he said.
Replying to a question, Katti said he would welcome if Ramesh Jarkiholi came to the BJP.
New government will be formed by the BJP in Karnataka by next week. How it will be formed, why it will be formed, don't think about it. When it is formed we will tell you, he added.
Karnataka Pradesh Congress Commitee President Gundu Rao asked Katti not to confuse people by making such illusionary statements.
If it doesnt happen, Katti will have to resign if he has guts, he told reporters.
Reacting to Rao's comments, Katti claimed that already eight to ten (Congress-JDS) MLAs were ready to resign.
"So as a party with 104 MLAs in the 224 member assembly, Im confident we can form the government," he said maintaining that the Congress-JDS government would fall "100 per cent".
Yeddyurappa said the BJP had nothing to do with the disgruntlement among the MLAs of the ruling combine.
"...if they are fighting internally, lets wait and watch what will happen at the end...till now no one has contacted us, nor we have contacted anybody and we don't require it also..." he told reporters here.