The Labour leader said he was against strikes in the Black Country and Staffordshire, where ambulance workers and nurses are balloting for industrial action over pay and conditions.
Sir Keir was asked if he would back strikes during a visit to Bilston, where he met with staff at Acorns To Oaks Financial Services.
In an intervention that risked the ire of the party's hard-left, he told the Star: "I don't want the strikes to go ahead, let's be clear about that.
"I don't think anybody working in the NHS or on the railways wants to go on strike. It is a matter of last resort and they themselves lose money for being on strike, so I want it resolved.
"The Government has put people in a very difficult position, because we have got wages that have been stuck for a very long time and prices going through the roof.
"What I want to see happening is a resolution of the individual issues, but more importantly, a government that is capable of stabilising the economy and dealing with the cost of living crisis.
"Otherwise this is going to be an endless cycle and in six months there will be another round of disputes because prices will have gone up again."
Pressed on whether supporting workers was one of the key duties of the Labour Party, Sir Keir said: "My job is different to the job of a trade union leader.
"My job is to make sure we have a Labour government, and that's the single most important thing we can do for working people."
Rail workers across the region have been involved in strikes for months while Metro staff are set to hit the picket lines from October 15.
In an interview with the Star, Sir Keir also addressed issues including the economy, Brexit and immigration as he bids to win back seats at the next general election.