The owner of the Boston Globe has extended talks with unions to try to save one of America's best-known big city newspapers from closure.

The owner, the New York Times, is asking Boston Globe staff to accept lower salaries and cuts in pension and redundancy benefits.

It has said it will file a notice with the government that it will shut the paper if there is no agreement.

The Boston Globe is expected to lose $85m this year.

Online competition

The owners want the unions to agree to $20m (£13.4m) in money-saving measures.

Guaranteed jobs for life are expected to be a sticking point, with the unions saying they are not negotiable.

The biggest union, the Boston Newspaper Guild, said it had offered more than $10m in concessions.

There was originally a Friday deadline for agreement, which was extended after some progress was made.

The Boston Globe is the latest title to find itself crushed between a variety of forces, including falling sales, rising costs and declining advertising revenues, the BBC's Kevin Connolly in Washington says.

Our correspondent adds that the internet is the source of most of the American newspaper industry's problems: demand from readers forces them to publish information online instantly and consumers are then reluctant to pay to see the same news in print the following day.

At the same time, internet sites offer cheap - and sometimes free - competition for the classified advertising which once kept the industry going.

With no new business model in sight to resolve those problems it seems inevitable that more titles will close in future, our correspondent says.

At least 12,500 jobs have gone in US print journalism in the past two years.