Iain Duncan Smith has defended plans to get the sick and disabled back to work amid allegations that he is "punishing" society's most vulnerable.
The Work and Pensions Secretary insisted being employed was like a "health treatment" and could help make people better.
He also denied that he had a target of taking a million disabled people off benefits, arguing it was sensible to ask whether individuals could do some work rather than writing them off altogether.
In an interview with the Press Association after delivering a speech in central London, Mr Duncan Smith said: "The present system of sickness benefit has a problem. It has at its heart a test that asks a simple question - are you too sick to work or can you work full time?
"My answer is, that is the wrong question. Labour started this process and it has never quite worked in that regard.
"Quite often people want to work if they are on the sickness benefit, but they cannot work because they are not allowed to otherwise they lose their benefits.
"So we want to look at a process that allows us to be able to assess them properly, ask what can you do not just what can't you do.
"And actually then be able to say, 'look we want to get the right support for you and enable you to stay in touch with the world of work'.
"Work is actually a health treatment in a sense. Those who are in work tend to be better and those who are out of work, on sickness benefit, tend to get their conditions worse.
Asked how he would reasssure Employment Support Allowance (ESA) claimants that they would be fairly treated following heavy criticism of work capability tests, Mr Duncan Smith said: "The system will be about what can you do rather than what can't you do. That's the big change I want to make.
"I want to feel that we are saying to people, so you have a particular problem, what does that mean for you in terms of work?
"Can you do certain hours, can you do certain types of work? We will figure out what you can do and then help you get jobs that are able to do that."
Mr Duncan Smith denied that he was committed halving the number of disabled on ESA, insisting it had been Labour ministers who suggested a million claimants could be taken off the roster in 2008.
"I'm not in that prediction game. I just think the whole objective here is to save lives, to help them get better lives," he said.
In the speech - which media were not allowed to attend - Mr Duncan Smith said: "We know there remains a gap between the employment rate of disabled and non-disabled people.
"We want to ensure everyone has the opportunity to transform their lives for the better by getting into work.
"That's why, as part of our one nation approach, we have committed to halving this gap."
The work capability assessment system that determines if someone will receive the employment and support allowance (ESA) has been dogged by controversy since its introduction under Labour.
Mr Duncan Smith said ESA was supposed to reduce the number of people on incapacity benefits by one million, but since 2010 there has been a fall of just 90,000 - and plans to reform the process would now be drawn up.
Nearly one in four jobseeker's allowance claimants have a common mental health condition and need more support to find, and stay, in employment, he added.
Mr Duncan Smith said: "We need to look at the system and in particular the assessment we use for ESA - and I want to look at changing it so that it comes into line with the positive functioning of Universal Credit, and as such is better geared towards helping to get people prepared for and into what work they may be capable of, rather than parking them beyond work.
"We need a system focused on what a claimant can do and the support they'll need - and not just on what they can't do."
He added: "Nearly 11 million adults in the UK have a common mental health condition and people are much more likely to fall out of work if they do.
"We also know that being out of work for four weeks or more can actually affect people's mental health, even if the original reason for ill health was a physical one."
At a campaign rally in London later, shadow health secretary Mr Burnham will say: "It's clear that Iain Duncan Smith is now preparing a new attack on disabled people to cover for his own failures on social security.
"Talk of cutting support for people who are simply not able to work will strike fear into the hearts of many vulnerable people.
"The cruel and crude approach of the Tories has already driven many people to despair and this new drive will cause even more anxiety."