NEW YORK (AFP) - US bookseller Barnes & Noble said Thursday it had ended a partnership with Microsoft for its Nook tablet computers, as the retailer prepares a spin-off of the unit.

B&N said it agreed to buy back the stake from Microsoft, which in 2012 agreed to invest US$300 million (S$396 million) in the Nook division.

The companies "have agreed to terminate their commercial agreement including any associated obligations for international content acquisition and sale," said B&N statement.

"Such termination will allow the company to continue its rationalization of the Nook Digital business and enhances Barnes & Noble's operational and strategic flexibility." Nook has had a difficult time in a tablet market led by Apple, Amazon and Samsung, but earlier this year agreed to make a co-branded tablet with the South Korean electronics giant.

B&N separately said it posted a profit of US$12.3 million on revenues of US$1.7 billion in the previous quarter, with the Nook division seeing an operating loss of US$38 million.