(Reuters) -- Blackstone Group LP has agreed to invest more than $800 million in NCR Corp that will give it the equivalent of more than a 15 percent stake in the automated teller machines maker, a source familiar with the matter said on Wednesday.

Duluth, Georgia's NCR plans to announce details of the deal with Blackstone, the world's largest private equity firm, by Thursday, the source said, asking not to be identified ahead of any official announcement.

Blackstone declined to comment, while NCR did not respond to a request for comment.

Blackstone held talks to acquire NCR outright earlier this year but could not agree on terms, people familiar with the matter have previously told Reuters. The Wall Street Journal first reported on the minority stake investment on Wednesday.

(Reporting by Liana B. Baker in New York; Editing by Lisa Shumaker)