The agreement was due to expire at the end of this month.
"The extension, which will extend the terms of the existing agreement, will provide further time for discussions regarding the contract renewal," said De Beers in a brief statement.
De Beers brought the Diamond Trading Company (DTC) to Botswana under the current deal, which also saw paved way for the country to receive 15% of the total Debswana output for sale by the state-owned Okavango Diamond Company.
Reuters reported last August that the coronavirus pandemic was expected to delay the conclusion of a new sales deal.
The country's minerals permanent secretary, Mmetla Masire was quoted saying at the time that there was no guarantee that they will renew a new 10-year sales agreement with De Beers before the end of December.
He said then that although Gaborone had resumed talks with De Beers, travel restrictions had slowed progress.
The extension of the current sales agreement will put a dent on President Mokgweetsi Masisi's plans to boost a young diamond polishing and cutting industry.
Mathew Nyaungwa, Editor in Chief of the African Bureau, Rough&Polished