TORONTO -- Thomson Reuters Corp. says it is offering to buy back up to US$9 billion of its outstanding common shares, representing about 31 per cent of its issued and outstanding shares.

The company says it will use some of the money it will receive from the sale of a majority interest in its financial and risk business to private equity funds managed by Blackstone.

The deal is worth about US$17 billion and expected to close on Oct. 1. The share offer is conditional upon the deal closing.

By buying back its shares, a company reduces its equity base, spreading profits over fewer shares and increasing its earnings per share, a key ratio used by financial analysts.

The shares will be purchased through a "modified Dutch auction" that will see shareholders who wish to sell tender their shares.

The company says it will pay between US$42 and US$47 per share, which is between 0.4 and 11.5 per cent higher than the company's volume weighted average price on the New York Stock Exchange over the past 20 trading days. The offer begins today and is expected to be completed on Oct. 2.