US pharmaceutical giant Pfizer has said that it remains open to a hostile takeover of AstraZeneca after its sweetened bid for the Anglo-Swedish drugmaker was rejected last week.After being asked whether Pfizer would take an offer directly to AstraZeneca's shareholders, Chief Executive Ian Read told analysts that the board is "considering all our options on how we progress these discussions"."We are very disappointed with their unwillingness to engage in conversations and believe it is in the best interest of both companies and AstraZeneca and Pfizer shareholders that we pursue a friendly negotiated transaction that can be recommended by both our boards."On Friday, Pfizer lifted its take over offer by 7% to 5,000p per share, valuing AstraZeneca at around £63bn. However, the latter group quickly rejected the offer, saying that the new terms were "inadequate" and "substantially undervalue" the company.May 26th is Pfizer's so-called 'put up or shut up' deadline which requires it to either make an offer for AstraZeneca or walk away, unless both parties agree to an extension. If the deadline passes, the US firm will have to wait six months before making another bid.Pfizer Chief Financial Officer Frank D'Amelio told Reuters in a telephone interview that "any option [regarding a takeover] you can think of would be an option"."What we really need is to have AstraZeneca engage with us [...] need to be able to do the right kind of analytics that need to get done," D'Amelio said.BC