The US government continued to push for Microsoft, the world's largest software company, to be broken up last night in the latest round of the legal battle.

In a 50-page document expected to be filed after stock markets closed in New York, the US justice department rejected the company's plea for far weaker sanctions on its anti-competitive behaviour. Both sides are due to present their arguments to Judge Thomas Penfield Jackson in Washington next week.

Last month, Judge Jackson ruled that Microsoft had broken American anti-trust laws by abusing its dominance of the personal computer market. He had indicated a desire to finish the case soon, possibly by this summer. But Microsoft has asked for an extension until December to prepare its case against the government's proposals.

Yesterday's filing was expected to outline the government's view of a prolonged hearing. Separately, official financial records for the US presidential candidates identified George W Bush, the Republican candidate, as a Microsoft shareholder.

The Texas governor has criticised the government's campaign against Microsoft for going beyond laws designed to stamp out predatory pricing.

Dan Bartlett, a spokesman for the governor, said yesterday the shares were in a blind trust and were therefore managed without the governor's knowledge by Northern Trust, a fund management group.

The shares were thought to be worth just over $100,000 at yesterday's stock market price. The financial statement filed earlier this month revealed that Mr Bush's assets include a diversified trust worth more than $1m as well as a 1,500-acre ranch of similar value.