Speaking to reporters after chairing a crisis meeting with Cabinet ministers, Cameron said the threat of thousands of job losses was "very difficult" and that the government would do "everything it can" but warned there were "no guarantees of success".
Cameron, who cut short his Easter break in Spain and rushed to London, said nationalisation was not the answer but the government was "not ruling anything out".
The Board of Tata Steel decided on Tuesday to decide on the future course of action in a bid to steer its embattled operations in Europe out of the rut, which face supply glut, increase in cheap imports from China amidst a continued weakness in demand in the European markets.
Shadow chancellor John McDonnell said the government should "bring forward the support that was expected in this budget and didn't happen" about reducing business rates, which he said were "five to seven times" higher in the UK than Europe.
Labour Party has urged ministers to "get a grip" and act now to help the steel industry.
It is understood the government wants reassurance Tata Steel will not close its plants before a buyer is found, the BBC reported.
Tata Steel's UK business - which directly employs 15,000 workers and supports thousands of others - includes plants in Port Talbot, Rotherham, Corby and Shotton.
Talk of nationalising the works has been downplayed but the government, which says it is considering "all options", may offer to help to engineer a sale.
"There was anxiety in government that Tata Group, the plants' Indian parent firm, wants to shut down its plants rather than sell them to a competitor, and ministers have been unable to secure a promise from the firm over how long it will allow the plants to remain open," the report said.
Labour union, Unite general secretary Len McCluskey said the UK was in the grip of an "industrial crisis of enormous proportions".
McCluskey also warned Tata against a "fire sale" of its UK steel plants.
Shadow chancellor John McDonnell said the government "should nationalise to stabilise" saying this would involve covering the plant's costs in the short term to help a new buyer turn it around.
Business Secretary Sajid Javid, who has cut short an official visit to Australia to return to the UK, said nationalisation was "not a long-term solution".
It is understood the government is looking at offering loan guarantees to potential buyers and much tighter rules on procurement to ensure major British projects are obliged to buy British steel, the report added.
Cameron has also spoken to Welsh First Minister Carwyn Jones to offer his support at an "extremely worrying time".
A government spokesman said Thursday's meeting - being attended by ministers and senior officials from the Treasury, Department for Business, Cabinet Office and Welsh Office - would focus on providing a "sustainable long-term future" for the steel sector.
He said the government had been in "disarray" and "chaos" and needed to "get a grip", repeating calls for MPs to be called back from the Easter recess.
