The Cabinet minister responsible for pensions has refused to in the latest indication that the policy could be under threat.
Work and Pensions Secretary Damian Green said that the Government would need to look at the state of the economy before it could commit to keeping the triple lock, which guarantees state pensions will rise by at least 2.5% every year.
He said it was "too early to say" whether the Tories would commit to keep the policy in the next general election manifesto.
The mechanism guarantees that the state pension rises by a certain level - which means it increases annually by the highest of average wages, inflation, or 2.5%.
But Philip Hammond used his Autumn Statement to signal that it may not be immune from cuts in the longer term.
The Chancellor said "as we look ahead to the next Parliament, we will need to ensure we tackle the challenges of rising longevity and fiscal sustainability".
On ITV's Peston on Sunday, Mr Green was asked whether that meant the triple lock was under threat and said: "I think it's far too early to start thinking about what happens in our manifesto for the next election, the triple lock is guaranteed until 2020.
"My personal view is that the debate is often a bit binary and what it leaves out is one of the tremendous successes, this is a non-partisan point, it's happened under governments of all types, that in the 1980s, 40% of British pensioners were living in poverty. That figure is now down to 14%. Now that's a huge social advance which we don't celebrate at all."
He said it would be "premature" to decide on the future of the triple lock, adding: "We'll need to see what happens to the economy between now and 2020 apart from anything else."
Mr Green said it would be "crude" to say all pensioners had done well out of the system while younger people had done badly.
He also defended the Government's welfare cuts, insisting that the measures were aimed at encouraging people into work.
The Chancellor used his Autumn Statement to cut the taper rate - the amount of Universal Credit withdrawn for each £1 earned above the threshold - from 65% to 63%, but critics said the measure did not go far enough to mitigate previously announced cuts to the benefit.
Mr Green said: "We're giving back to a wider group of people, and it specifically encourages people to progress in work. I think that, when you've got historically low unemployment levels that the next group of people you need to help are people who are probably not working very many hours to encourage them to take more and more work as it's available, as well as encouraging people who are not employed into work."
Cuts to the Employment Support Allowance would go to support people who are able to work find a job, he insisted.
"We are losing a lot of potential, a lot of people who want to work and could work are not being helped well enough into work so the money that's freed up from that will enable us to spend a lot more on helping people with a long-term health condition, with a disability to work," he said.
Shadow chancellor John McDonnell said doubts over the Conservative's commitment to the triple lock mean pensioners are now unsure of their futures.
He told the Murnaghan programme on Sky News: "Pensioners now, who as a result I believe of the Labour government that was in place, actually have been lifted largely out of poverty, many of them still struggle but we have improved the lot of pensioners in our society dramatically, particularly under a Labour government.
"But now the triple lock is threatened and as a result of that what we are seeing is pensioners fearful about their futures."