(Changes sourcing)

Feb 14 (Reuters) - Blank-check companies backed by buyout firm Warburg Pincus and billionaire real estate investor Barry Sternlicht will take security services firm Allied Universal public in a $20 billion deal, according to a source familiar with the matter.

The deal will involve three special purpose acquisition companies (SPAC) - Warburg Pincus Capital Corp I-A WPCA.N , Warburg Pincus Capital Corp I-B WPCB.N and Sternlicht's JAWS Estates Capital LLC.

The SPACs are currently in talks to raise a so-called private investment in public equity (PIPE), said the source, asking not to be identified as the information was private.

A representative for Warburg declined to comment, while JAWS Estates did not immediately respond to a Reuters request for comment.

California-based Allied Universal, which is already owned by private equity giant Warburg, provides integrated security services to help clients secure their businesses. The deal talks were first reported by Bloomberg News.

SPACs are shell companies that raise capital through an initial public offering to merge with a private company, which then becomes publicly traded as a result.

(Reporting by Niket Nishant and Mehnaz Yasmin in Bengaluru and Chibuike Oguh in New York; Editing by Shinjini Ganguli)