Steel unions say they have a commitment from Tata to secure the future of jobs and production at Port Talbot and other steelworks across the UK.
A number of "significant" measures include keeping two blast furnaces at the South Wales plant for five years, a commitment to seek to avoid compulsory redundancies for a similar period, a 10-year investment plan of £1 billion and consultation on replacing the pension with a defined benefit scheme.
Unions said after a meeting in Port Talbot that the commitments on jobs, production and investment were welcome, although the pension proposal was "worrying".
The future of Tata plants has been in doubt since its UK business was put up for sale in March.
The Indian conglomerate put the sale on hold in the summer as it considered a tie-up with German steelmaker ThyssenKrupp.
Tata employs thousands of workers, including more than 4,000 at Port Talbot, and others at Trostre and Shotton in Wales, Corby, Hartlepool and at sites in the West Midlands.
Roy Rickhuss, general secretary of the Community union, said: "The past year has been incredibly difficult for steelworkers and their families. When Tata announced in March that they planned to sell the steelworks, no-one knew if they would have a job by Christmas.
"This proposal would secure jobs for years to come and bring serious investment not just to Port Talbot but to steelworks across the UK.
"Reaching this stage of the process is a credit to the hard work of our members, who never gave up the fight to 'Save Our Steel' – it was their jobs on the line and it has been their campaign that has brought Tata to this position.
"This is not the end of the process and it will be for all our members to now vote on this proposal. We will continue to work closely with Tata and all levels of government as we seek to build a sustainable future for Britain's steel industry.
"We recognise that today's announcement does not cover the Speciality Steels business in South Yorkshire or the SAW mills in Hartlepool. We will continue to work hard with the companies involved to secure the investment necessary to ensure those businesses grow and that our members are protected."
Unite's national officer, Tony Brady said: "Today's news it a step in the right direction for our industry but there is still a lot more that government can and must do. The Tories say they are committed to an industrial strategy, but steelworkers need more than warm words.
"The commitments made today by our reps must now be followed by a commitment from the Government that they will hold Tata to their word and ensure jobs are protected. The UK steel industry supports our whole manufacturing sector and it is vitally important that the future of that industry is secured for generations to come."
GMB's national officer, Dave Hulse said: "This agreement would mean the blast furnaces at Port Talbot keep making steel and that steelworks across the UK get the investment they need to compete in the future. We've fought hard to save jobs and today's agreement is a credit to our members.
"Today's news is a step forward, but there is still much to be done. We will continue to fight for a level playing field for our industry; for action on energy costs, on business rates, and on the dumping of foreign steel."