South Australian steelmaking business Arrium is to be sold to a British company and not the Korean consortium identified as the preferred bidder, the state's Premier Jay Weatherill has confirmed.

The business will be sold to Liberty House which is part of London-based GFG Alliance, with all Whyalla steelworkers expected to keep their jobs.

"The sale of the whole of the business is a dramatic victory for us here in SA," Mr Weatherill said.

"Any self-respecting nation needs its own capacity to create steel products. This is about building our nation, it is about building our national infrastructure and we cannot be beholden to other countries for a steel industry."

The sale is subject to approval by the Arrium Committee of Creditors, which meets next week, and the Foreign Investment Review Board.

The iron-ore giant Arrium went into voluntary administration in 2016, with debts of more than $4 billion.

Arrium's administrator KordaMentha said it had signed a "binding agreement" with GFG Alliance to sell the steelmaking and mining company.

It said the company owned by the British Gupta family had submitted a modified offer on Tuesday night.

"Taking all factors into consideration, including the timeframes required to complete a sale, KordaMentha and our sale advisers Morgan Stanley decided that GFG was an option superior to the conditional offer of the Korean alliance with whom we were negotiating," administrator Mark Mentha said.

'A positive future for Whyalla'

Mr Weatherill said he and Treasurer Tom Koutsantonis would meet with representatives from Liberty House tomorrow, and said the announcement ends 15 months of uncertainty for the Whyalla workforce.

"This is a great victory for Whyalla. An extraordinary victory for South Australia and a very important victory for our nation," he said.

After uncertain times, Arrium's workforce is being promised there will not be job losses from the deal. ( ABC News: Simon Christie )

"The other wonderful thing about this decision is that the company themselves are pledging to retain all of the workforce at the Whyalla steelworks and promising to invest in upgrading the steel works in the future."

Federal Treasurer Scott Morrison welcomed the outcome, saying the process to approve the sale would be done "speedily".

"We have already been in a position to agree the conditions around the Foreign Investment Review Board process," he said.

"I expect to sign off on that later today which I think will give the added certainty for the workers in Whyalla and the community in Whyalla which demonstrates a very positive future for them."

The Korean consortium, headed by Newlake Alliance Management and JB Asset Management, and supported by POSCO, was selected as the preferred bidder last month.

An exclusivity period granted to Newlake expired on Friday with no deal reached.

SA Treasurer Tom Koutsantonis said due to the consortium's "internal issues" it was unable to make a share agreement and over the weekend Liberty House came in "with a strong bid".

KordaMentha said once the sale was completed it would continue with the business of administration, including finalising returns to creditors.

The cost of the sale has not been disclosed and the deal is expected to be finalised by the end of August.

It is understood GFG's bid is not conditional on any extra funding from the State and Federal Governments than that already on offer.

Announcement secures thousands of jobs, GFG says

GFG's bid is also the third submitted by the company, which said its acquisition of Arrium would guarantee 5,500 jobs in Australia.

Chief executive Sanjeev Gupta said Arrium fitted in "perfectly" with GFG's strategy, adding "we believe it has an exciting future".

Mr Gupta said GFG would continue to explore business opportunities in Australia, including in the renewable energy and mining sectors.

"I would like to thank all stakeholders who have worked tirelessly alongside me for over a year on this acquisition," he said.

Whyalla mayor and former Labor MP Lyn Breuer said news of the announcement was "such a relief" for Whyalla.

"We've been through a terrible time in the last 15 months... a lot of uncertainty, a lot of doom and gloom initially," she said.

"This is a bit of a surprise that it's Liberty but certainly very, very welcome.

"They have a very strong mining record and certainly have steelworks around... we're very comfortable they'll be able to do the same for us.

"I said a few weeks ago that we had the champagne in the fridge but we wouldn't pop the corks, but I'm pretty sure we might pop them perhaps next week some time."

SA Opposition Leader Steven Marshall also responded favourably.

"After so much doubt and stress about the future of Whyalla's steelworks, this would be a tremendous relief for the workers and their families," he said.