Iain Duncan Smith has admitted making mistakes in the plans to roll out flagship benefit reforms and said the original 2017 deadline had been "artificial".
Universal Credit is now being rolled out to families in the north west of England but it is expected to take until 2019 to put all claimants on to the system, the Work and Pensions Secretary said.
He said the original plans for rolling out the welfare changes, which combine benefits into a single payment, had been wrong and he had taken the decision two years ago to "reset" the timings of the project because he recognised that it needed a longer timescale.
The reforms have come under repeated criticism, including from the National Audit Office, which has previously said the project suffered ''weak management, ineffective control and poor governance''.
But, speaking on BBC Radio 4's Today programme, Mr Duncan Smith dismissed claims that the scheme was beset by problems.
"You've said that it's constantly dogged," he said. "That's not correct.
"I decided two years ago, having had some outside work look at this, that the wrong way to roll it out, as was originally planned, was to roll it out like tax credits, which as you may remember had been a disaster. They crashed and 400,000 people didn't get their payments.
"I hope anyone listening will recognise that if we do it carefully and we land it safely, they are far better off than trying to rush something for a simple deadline, which actually was artificial in the first place."
All claimants in the north west of England will be on it by the end of the year and the national roll-out will begin next year.
Mr Duncan Smith said: "This is not about low-hanging fruit. We have deliberately set out to roll it out so that each bit of it is tested. There is nothing low-hanging about an individual looking for work needing better support.
"On the deadlines and dates, we've been very clear about this, that actually we plan to have completed all the legacy benefits by possibly the end of 2017 and should have complete, everybody on it in 2019.
"There are some big, big changes and overall these changes in Universal Credit mean something like three million households will gain an average of £177 a month than they do under the current system."
Mr Duncan Smith insisted that the Government "had already been doing an awful lot" to reform the way benefits are claimed by European Union migrants.
"What we have done is talk to all the other countries about a simple system that says you are the responsibility of your own country until you have actually established yourself as resident and eventually contributing towards that system."
Mr Duncan Smith announced to the Conservative conference in September that he was planning to accelerate the national roll-out of Universal Credit to every community in Britain by the end of 2015/16.
The Department for Work and Pensions said today that this will mean one in three of the country's Jobcentres taking claims for the new benefit by spring 2015.
And six Jobcentres in the North West are now taking claims from couples with children and lone parents, who will receive support for childcare via Universal Credit for the first time. Payments will initially cover 70% of childcare costs, rising to 85% in 2016, as announced in the March Budget.
Universal Credit is already available to single and couple claimants in more than 80 Jobcentres in England, Wales and Scotland and will be available in nearly 100 Jobcentres by Christmas, said the DWP.
The department cited research suggesting that claimants find Universal Credit easier to understand than the previous array of benefits and considered that it provided better financial incentives to work.
But shadow work and pensions secretary Rachel Reeves said the Universal Credit programme had become " a complete shambles".
"The latest figures from the Department for Work and Pensions show just 17,850 people are claiming Universal Credit - less than 1% of the million people Iain Duncan Smith said would be on the new benefit in April 2014," said Ms Reeves.
"Labour wants Universal Credit to succeed but the Government's mishandling of the programme has led to huge waste and delays with over £130 million of taxpayers' money wasted on failed IT. It's another example of Tory welfare waste.
"A Labour government would pause Universal Credit for three months to examine whether the programme can be rescued from the shambles David Cameron's Government has left it in."