Analysis By Nick Assinder Political Correspondent, BBC News website

As Tony Blair took to the stage for his latest monthly press conference, two images were clamouring for voters' attention.

Monthly briefing

The first was the prime minister setting out, with a blizzard of statistics and a PowerPoint presentation, just why, in key areas, the NHS had never been better.

He avoided using the sort of language his health secretary, Patricia Hewitt, used and which has so infuriated nurses and the unions.

But his message was clear - reform is hard, there will be some losers, but the overwhelming picture is positive and, in any case, it is unavoidable if the NHS is to be modernised for the benefit of patients.

The other image was of nurses and union leaders pledging to fight, with strike action if necessary, threatened job losses and cuts to NHS services.

That combined with opposition leaders repeating their claims that the government has fatally mismanaged the NHS which has seen the admittedly large sums of money poured into the service draining away through pay hikes and bureaucracy.

Job cuts

One paints a picture of a health service doing better than ever before - as suggested by Ms Hewitt - and with patients already feeling the benefits of reforms.

The other is of an NHS in crisis, struggling and often failing to deal with those government reforms which, it is claimed, will see job cuts, ward and hospital closures and patients losing out.

Health workers fear closures

It is a clash which has some faint echoes of the confrontation between government and public service workers that helped bring down the last Labour government in 1979.

It has not entered that territory yet, but the sounds coming from both sides suggest there is potential for these opening skirmishes in the battle over the future of the NHS to escalate.

The prime minister is clearly determined to press ahead with his reforms and used his press conference to send out a plea for some "balance" in the reporting of the issue.

Local elections

Time and again he insisted he was not playing down the problems affecting some areas of the service.

But he also repeated "the facts" that waiting lists and times, and cardiac and cancer care were "the best the NHS has ever had".

"The facts speak for themselves," he declared. "Let's just have a proper sense of balance".

The unions and nurses leaders appear equally determined to stand their ground.

Just how voters chose between the two competing images - particularly with local elections just over a week a way - is the crucial question.

The answer is probably simple. They will judge not on the claims and counter claims, but on personal, purely subjective experience, either their own or their friends' and families'.

And if the prime minister is right in his assertion that things have massively improved since 1997, he has nothing to worry about.