Newspaper editors are to attend a Downing Street summit to make their case for resisting the legally-backed press regulation called for by the Leveson Report.
Senior industry figures will meet Culture Secretary Maria Miller to set out progress towards the creation of a new independent watchdog.
But she warned them on Monday night that any failure to unite behind a sufficiently tough and independent self-regulatory body could leave the Government no choice but to legislate.
Prime Minister David Cameron, who will attend part of the meeting, has expressed "serious concerns and misgivings" about Lord Justice Leveson's recommendation of legislative underpinning.
With Labour and the Liberal Democrats united in favour, his own backbenches split and phone-hacking victims leading a campaign for full implementation, he is under huge pressure. An online petition launched by campaign Hacked Off has so far attracted more than 135,000 signatures in favour of statutory underpinning.
Ahead of the gathering at No 10, Press Complaints Commission chairman Lord Hunt claimed the support of 120 publishers, representing 2,000 editors, for a new independent regulator. He said it was not necessary to back that up with legislation because newspapers could instead sign legally-enforceable membership contracts.
Opening a Commons debate on the Leveson proposals, Mrs Miller told MPs the status quo was not an option in the light of the PCC's failure to prevent abuses by elements of the press.
"Change can either come with the support of the press or - if we are given no option - without it. Be in no doubt that if the industry doesn't respond, the Government will," she said. Action "would include legislation" if industry proposals fall short of Leveson's principles that a new regulator must be truly independent and able to impose big fines on newspapers, she said. "We will not accept a puppet show with the same people pulling the same strings."
Officials at Mrs Miller's Culture Department are drawing up a draft Bill to enact Leveson's recommendations in full. But she has indicated that she expects it to provide confirmation of concerns about the complexity and potential negative consequences of extending statutory controls over the press.
Any legislation could be amended by future administrations to muzzle the press and would harm the UK's reputation abroad as an advocate of free speech, she told MPs.