Manulife Financial Corp (MFC.TO), Canada's biggest life insurer, on Thursday played down reports that it is exploring an initial public offering of U.S. unit John Hancock.

"It's all market rumor and speculation as far as I'm concerned," Chief Financial Officer Steve Roder said in an interview.

The Wall Street Journal reported in July that Manulife was under pressure from some shareholders to make the move after years of disappointing results at the unit.

Manulife acquired John Hancock for $15 billion in 2004 in a deal that doubled the size of the insurer. There has been speculation in recent years that the business could be sold as the company has made Asia its priority for growth.

The company has said it would consider selling some businesses that are hindering growth.

"For the last 18 months or so, we've highlighted to our investors that we are always considering how we can optimize our balance sheet and accelerate the growth in (return on equity)," Roder said.

On a conference call with investors on Thursday, outgoing Chief Executive Don Guloien said Manulife had "some challenging blocks of legacy business" and "regularly investigates all opportunities of improving shareholder value".

When asked if he thought an IPO of John Hancock was a non-starter he replied: "No, I don't think there are any non-starters. When you run a public company you've got to look at every perspective in a dispassionate way. That's not to suggest that we would do that or that's it's easy to do. The ultimate determination would be is it good for building shareholder value? That would be the criteria our company would use."

Manulife and rival Sun Life both reported second-quarter earnings that beat analyst expectations after the market closed on Wednesday, benefiting from strong performances in Asia.

Sun Life was up 0.6 per cent in early trading on Thursday with Manulife down 1.8 per cent.

Guloien is due to retire as CEO on Oct. 1 and will be replaced by Roy Gori, who currently heads the group's Asia operations.