BlackRock's ( BLK) expected deal to buy Barclays Global Investors from U.K. bank Barclays ( BCS) is likely to be announced as early as Thursday, the Wall Street Journal reports, citing people close to the matter.

Money manager BlackRock is expected to pay about $13 billion for the asset-management unit, and Barclays could retain about a 20% stake, the Journal and other reports this week have said.

Barclays could get a seat on BlackRock's board as part of the deal, the Journal reports. BlackRock is expected to fund a portion of the purchase from sovereign funds in the Middle East.

Combined with BGI, BlackRock would be the world's largest money manager, with roughly $2.8 trillion in assets under management, according to the Journal.

Barclays on Monday confirmed it has held talks with BlackRock for the BGI business, but also said it has received proposals for BGI and its iShares business from a number of parties.

Barclays reached an agreement earlier this year to sell iShares, which specializes in exchange-traded funds, to CVC Capital Partners for $4.4 billion. But a "go shop" clause in the agreement gives Barclays until June 18 to get a better deal for iShares or BGI and pay a $175 million break-up fee to CVC.