HP has extended the deadline for Mercury Interactive shareholders to tender their shares in favour of the companies' proposed $US4.5 billion merger.
As of midnight US Eastern time on Thursday, when the offer was set to expire, 67.8 million shares had been tendered in favour of the deal, HP said. The deadline had been extended to midnight on September 28.
An HP spokesperson in the UK couldn't immediately say how many shares were required to secure the deal.
HP announced in July that it planned to buy Mercury in a move to strengthen its menu of IT management software and services. The combined company would be a stronger competitor to CA and IBM.
HP has since been hit by a scandal over how it sought to identify the source of leaked information from its board meetings. The company has acknowledged hiring a private investigation firm that posed as suspect board members and journalists in order to access their private phone records.
HP chair, Patricia Dunn, is to step down over the scandal and California's attorney-general has said charges are likely to be filed.