Caretaker SA Premier Mike Rann has stared down his impatient colleagues and negotiated a deal to stay on as Labor leader until October 20.

After meeting premier-in-waiting Jay Weatherill this morning, he told a packed media conference in the State Administration Centre that he had brought forward his original plan to leave politics in March next year. He said he had not yet given any thought to retiring from parliament.

Rann said there had been “no pressing urgency to make transition to leadership right now”.

He said he never objected to the factions’ choice of Weatherill as his successor: “No doubt Jay has the skills and passion to lead.”

He revealed he had agreed to step down next year “if a suitable and agreed successor could be found”. When told last Friday week on the eve of a trade mission to India that a successor had been found, Rann said he had made a commitment to negotiate a timetable on his return from India. But the plan was scuttled, he said, when details of the meeting were leaked.

“I was disappointed with the selective leaking of details of that meeting … within minutes of it happening,” he said. “It contradicted previous commitments. My intention has been affected by events in the last 12 days.”

Rann, 58, is the state’s fourth longest-serving leader at nine years and 156 days. The October 20 date for his exit means he will pass Don Dunstan’s mark as Labor’s second longest-serving premier.

Rann said he had several commitments he wanted to complete before leaving office, including the new Royal Adelaide Hospital, the Adelaide Oval redevelopment and the “saving of Arkaroola from mining”. “I’ve got a couple of more things to do,” he said.

Naming the approvals of BHP Billiton’s $30 billion Olympic Dam expansion as the “most important” project, Rann said he would “conclude those negotiations”. Weatherill will become part of the negotiating team on the project from this week, he said.

Rann said he was putting the state first. “My clearest and highest obligation is to the people of south Australia,” he said, followed by the state government and then SA Labor in third place.

At the same media conference, Weatherill said the Labor Party was united behind his leadership and it was important to pay “proper respect” to Rann.

Weatherill said he looked forward to receiving Rann’s “extraordinary insights” in the role between now and October 20.