David Cameron will come under fresh pressure to nationalise the Port Talbot steelworks until a private buyer can be found as he holds face-to-face crisis talks with First Minister of Wales Carwyn Jones.
The Prime Minister insisted the UK is doing all it can to find a long-term solution for the giant South Wales plant and the Government would make it "as attractive as possible" to investors.
But Mr Jones said he would be asking Mr Cameron to provide an assurance that the Government would take Tata Steel's plants in Wales into public ownership until an investor comes forward.
Mr Cameron and the First Minister will meet in Downing Street for talks, along with Chancellor George Osborne, Business Secretary Sajid Javid and Welsh Secretary Alun Cairns.
Meanwhile Jeremy Corbyn will accuse the Tory administration of having an "ideological allergy to public ownership" which is preventing it from taking the steps needed to save the steel industry.
Ahead of the Number 10 summit, Mr Cameron said: "The Government is doing everything it can to find a long-term, viable solution to save the Port Talbot steelworks.
"At this morning's meeting, Carwyn Jones and I will look at how London and Cardiff can work together to make sure that the plant has a solid future and end the uncertainty for workers and their families.
"We remain fully focused on finding a buyer to run the steelworks and today's meeting is an opportunity to discuss what needs to be done to make this prospect as attractive as possible to investors."
As well as Port Talbot, Tata has four other plants in Wales - Llanwern and Orb in Newport, Shotton in Flintshire and Trostre in Llanelli.
Setting out his demands, Mr Jones said on Monday: "My message to the Prime Minister tomorrow is simple. These plants cannot close."
He will urge the PM to take action in Europe to tackle dumping of cut-price Chinese steel, infrastructure measures to boost demand for British metal and a commitment by the UK Government to take a stake in the firm, at least in the short term.
Mr Jones said: "Britain must remain a steel producing country and we must work together to achieve and maintain that. The Welsh Government has committed to doing what we can within our available powers and resources, and now its time for the UK Government to act.
"There are strong economic, moral and strategic reasons why we must continue to produce our own steel, and I will be making that argument very clearly - as well as asking for solidarity and support for our workforce.
"Steel producers in the UK need to operate on a level playing field with the rest of the world and I will be asking for assurances that the UK Government will negotiate a realistic tariff regime at European Union level to mitigate steel-dumping.
"I will also be seeking progress on major steel using infrastructure projects - such as the Swansea Bay Tidal Lagoon - which will provide much needed support for the industry in Wales.
"I will also be asking the PM to provide assurance that the UK Government will take Tata's plants in Wales into public ownership to allow enough time for a buyer to be found.
"The Welsh Government has put forward over £60 million towards securing a new buyer for Tata's operations in Wales. I now look forward to seeing what the UK Government is going to put on the table."
At a campaign event in Harlow, Labour leader Mr Corbyn will insist that the Government should put taxpayers' money into the industry.
He will say: "We are calling on the Government to accelerate investment for £35 billion of already agreed infrastructure projects and to build them using British steel.
"This industry is too important to our manufacturing economy and our security to fail. This Government's ideological allergy to public ownership is stopping it taking the steps needed to save steel.
"The Government must act now to protect the steel industry. It must take a public stake to guarantee steel's future and make sure that any financial support brings a return to the public."