Updated from 12:51 p.m. ESTTime Warner's ( TWX) AOL has offered to buy TradeDoubler, a Swedish online marketing company, for about $900 million in cash. AOL announced the bid in a press release early Monday. However, AOL likely will have to raise its offer after Alecta, a Swedish pension-fund manager and TradeDoubler's largest shareholder, rejected it, according to a report in The Wall Street Journal. TradeDoubler's board supports the deal, and holders of about 20% of TradeDoubler's stock have already pledged their shares, the press release from AOL said. TradeDoubler's stock trades on the Stockholm exchange. Time Warner shares finished Friday up 11 cents at $22.73. U.S. markets are closed Monday in observance of Martin Luther King's birthday.