Alun Cairns told MPs Tata agreed to a sales process due to government action.
But Plaid Cymru criticised Mr Cairns for not attending a crucial Tata board meeting in India in March.
Later, David Cameron said ministers would "work with any potential purchaser of the Port Talbot works which will safeguard steel jobs in other parts of the country".
The plant employs 4,000  workers directly.
Mr Cairns defended the government's handling of the steel crisis, in his first Welsh Questions session since being appointed secretary of state for Wales in  March.
He said ministers had been in close dialogue with Tata Steel for many months.
"It is due to the government intervention that Tata have agreed to a sales process rather than an immediate closure of its operations in Wales," he said.
Plaid Cymru's parliamentary leader Hywel Williams asked Mr Cairns why he missed the board meeting in Mumbai at which the decision to sell off its UK assets was taken.
"What stopped you? Was it the Cabinet pecking order? Was it indolence? Or was it just plain ignorance?" he said.
Mr Cairns replied: "Surely what the steelworkers want to see is where the government and the opposition work together, where the company and the unions work together in order to secure that long-term future."
Labour Shadow Welsh Secretary Nia Griffith demanded assurances that Tata Steel would not syphon off its most profitable lines to its plans abroad.
Mr Cairns said a positive engagement between the government and Tata had led to the decision to sell off the assets as a whole rather than to dispose of some of the more profitable assets.
Mr Cairns had earlier told MPs: "The steel industry is currently dealing with unparalleled global economic conditions and the UK is deeply concerned by the social and economic impact they are having in south Wales.
"Whilst we cannot change the status of the global steel market our objective remains to overcome the challenges and play a positive role in achieving sustainable future for the steel industry in Wales and across the UK."
UK ministers averted the immediate closure of Tata's Port Talbot steel plant, the Welsh Secretary has said.