(REUTERS) - Pfizer Inc may sweeten its offer for Britain's AstraZeneca Plc to more than 63 billion pounds (S$133 billion) and raise the cash portion of the deal, to kickstart negotiations, Bloomberg reported on Thursday.

Citing people with knowledge of the matter, the report said a new bid may value AstraZeneca at more than 50 pounds per share and could come as early as next week.

Pfizer disclosed earlier this week that it had twice approached AstraZeneca about a takeover, only to be rebuffed in both cases.

Pfizer officials could not immediately be reached for comment.