Jeremy Corbyn is resisting pressure from Labour MPs to commit the party to keeping the UK in the EU single market after Brexit.
As activists gathered in Brighton for the start of Labour's annual conference, 30 senior figures have written an open letter calling for the party to do whatever it takes to keep Britain in the single market and the customs union.
But in a high-profile TV interview kicking off the week's events, Mr Corbyn said Labour needed to be careful not to give up powers which it will need in government to deploy state support for industry.
An upbeat Mr Corbyn, who goes into the conference in an unassailable position just a year after facing an attempt to oust him as leader, said the Conservative Government was "running out of steam", while within Labour "the steam is rising, not falling, and the movement is stronger than ever".
He confirmed he had received unanimous support from Labour's ruling National Executive Committee to give greater power to party members, including by giving conference the final say on deciding policy.
In an interview with BBC1's Andrew Marr Show, the Labour leader repeatedly dodged the question of whether he would join picket lines on an illegal strike, but said he would "be with" workers demanding decent pay rises.
The 68-year-old veteran was reported by the Sunday Mirror to have said that he wanted to serve 10 years in Downing Street - something which could keep him in power until the age of 83.
However, he suggested in his TV interview that this was the period he thought Labour needed to push through its agenda.