Botswana and De Beers said they had agreed "in principle" on a new deal for diamond sales and to extend mining licences for their joint venture, ending months of tense negotiations that appeared to threaten their 54-year-old partnership.

The planned new sales agreement for rough diamond production covers 10 years while mining licences for their Debswana joint venture are set to be extended for 25 years, according to a short joint statement issued on Friday.

It was not immediately clear if Botswana would be getting a bigger share of Debswana's output as hoped for.

Botswana Mines Minister Lefoko Moagi did not immediately reply to a request for comment.

Under an agreement that expires on Friday, Debswana sells 75% of its output to Anglo American unit De Beers, with the balance taken up by Botswana's state-owned diamond trading company, Okavango Diamond.

Earlier on Friday, Botswana President Mokgweetsi Masisi, said both parties were making compromises to get a deal.

"We have seen De Beers starting to concede to our demands. Likewise, we have also been making concessions," Masisi told a community meeting.

An interim sales agreement is in place until the new pact is finalised, the two partners said in a statement.

"The transformational new agreements between Botswana and De Beers reflect the aspirations of the people of Botswana, propels both Botswana and De Beers forward, and underpins the future of their Debswana joint venture through long-term investment," the statement said.

In March, Botswana announced it would take a 24% stake in Belgian gem processing firm HB Antwerp in a move seen as designed to loosen De Beers' grip on the country's gems. Okavango Diamond plans to enter into a five-year agreement to supply rough diamonds to HB Antwerp as part of the deal.

Botswana, the world's second largest diamond producer after Russia by output, supplies 70% of De Beers' rough diamonds.

Diamond sales, almost entirely from Debswana, account for two-thirds of Botswana's foreign currency receipts and a fifth of its gross domestic product.

Debswana's diamond sales hit a record $4.6 billion last year, compared to $3.5 billion in 2021.

(Additional reporting by Felix Njini in Nairobi, Nelson Banya in Harare and Nilutpal Timsina; Editing by Edwina Gibbs)