The University of Adelaide and the University of South Australia (UniSA) have decided against a merger, following months of discussion between the two institutions.

Key points: The universities announced they were considering merging in June

The universities announced they were considering merging in June The aim was to get the combined institution into the world's top 100 universities

The aim was to get the combined institution into the world's top 100 universities They have announced merger plans will not go ahead

The two universities have been in talks over a proposal to combine the two institutions following an announcement in June.

University councils from both had endorsed a six-month period of collaboration to discuss the merger, and a joint report of the findings was due to be delivered by the end of the year.

In a joint statement, University of Adelaide chancellor Kevin Scarce and UniSA chancellor Pauline Carr said merger discussions "have ended at this time, rather than progressing to a decision in December".

"Right from the start, our universities identified key threshold issues and strategic risks which required agreement from both sides," they said.

"Ultimately, our universities were unable to reach agreement on the threshold issues and strategic risks.

"Rather than engaging in further exploration of a potential merger, we feel it is in each university's best interests to bring our discussions to a close at this time.

"We acknowledge and respect the hard work that has been done by both of our universities to date in exploring the potential for a merger."

Universities will continue separately

Both thanked their university communities including staff, students, alumni, business and industry stakeholders for their input during the process.

"As we said at the start of this process, both of our universities have unique histories and we have both evolved to meet the needs of each generation," they said.

"Those histories will continue, and at this time we will pursue excellence and serve the needs of the community as two distinct universities."

UniSA former chancellor Jim McDowell and vice-chancellor David Lloyd, and Adelaide University vice-chancellor Peter Rathjen and chancellor Kevin Scarce meeting about the merger. ( Supplied )

In separate emails to staff, students and alumni, the University of Adelaide appeared to be keen on a merger, but UniSA was not convinced.

Mr Scarce said his university's council remained confident that a merger "would be in the long-term best interests of the state".

He said thousands of staff, students and other stakeholders had provided feedback on the merger.

"The feedback we have received from our community has underscored the importance of the University of Adelaide's heritage and identity as the highest-ranking university in South Australia," he said.

UniSA vice-chancellor David Lloyd said his university's council had concluded that there was "not a compelling case to support a merger of the two universities and that consequently, the process of exploring a merger should cease".

"This decision allows each institution to focus on delivering its own independent strategy…"

In June, Mr Scarce and Ms Carr said a combined university could be "in the top few in Australia for size and scale; may place it firmly within the world's top 100; and have a reach that could make it one of the most international universities in Australia".

The University of Adelaide was founded in 1874 and has more than 21,000 students and 3,000 staff.

It has three campuses in total, in the Adelaide CBD, in Urrbrae, south of Adelaide, and in Roseworthy, north of Adelaide.

UniSA was founded in 1991 and has more than 31,000 students at six locations around South Australia.

A Flinders University spokeswoman said it was "business as usual" at South Australia's third university.

"We have not been involved in any merger discussions," she said.