Labour would "not make political capital" out of any U-turn on tax credits, shadow chancellor John McDonnell has said.
The shadow chancellor suggested his party could support a revised plan to cut tax credits if "real protection" is given to low-income families.
"I’ve written to George Osborne to say ‘I know what a U-turn looks like... We need a U-turn,’" he told the BBC's Andrew Marr Show.
"I've said to him: 'Look if you can change your mind on this, we will not make any political capital out of this."
Peers are threatening to block the £4.4 billion welfare squeeze when the House of Lords vote on Monday.
Labour is calling for the cuts to be delayed while independent analysis on their impact is carried out.
The party also wants at least three years of transitional help to be given to those affected.
"If the Lords do throw this out tomorrow and put it back to the Government, [if he] brings back a policy in which people are protected - not a political stunt - but a real protection, we will not in any way attack you for that - in fact we'll support you," he said.
In Mr McDonnell also said:
On the steel industry
Mr McDonnell reiterated his call for the Government to intervene in the British steel industry, which has suffered thousands of job losses in recent weeks.
Asked whether he would consider renationalising the sector: "Italy has turned the situation around - we need to be a strategic state, intervening when necessary."
On the state of the Labour Party
He dismissed the threat of a leadership challenge by backbench MP Simon Danczuk as "that's Simon being Simon".
He said Labour were leading the way in creating an "open, democratic and engaging" debate which is helping to "re-engage" generations of people with politics.
There is "no way" left-wing activists will be allowed to force moderate Labour MPs out, the shadow chancellor said.
Veteran MP Frank Field has spoken of his concerns that so-called "Corbynistas" will try to "purge" those to the right.
But Mr McDonnell said: