The owner of the Port Talbot steelworks has written to trade unions offering fresh talks amid a battle to delay plans to cut 2,800 jobs and suspend production at a site that has been in operation since 1951. The Guardian understands that a letter sent on Sunday afternoon by Rajesh Nair, the UK boss of Tata Steel, has offered a new round of discussions about future investments at the company’s plants in the UK, including Port Talbot. However, sources have said the offer to the National Trade Union Steel Coordinating Committee, which represents all three unions at the site in south Wales, is predicated on unions agreeing to suspend any future industrial action. Tata had originally planned to close the second of its two remaining blast furnaces at the end of September, while the process of shutting down the first is due to begin in the middle of this week. Other elements that will close include the harbour, sinter plant, ore yards and primary steelmaking, bringing to a halt more than 70 years of steelmaking in Port Talbot. The plans were brought forward after the Unite union announced indefinite strike action beginning on 8 July. Tata said it could not “safely and stably” operate the plant during any strike, and it has brought forward complete closure of the second furnace to as early as next Sunday 7 July. The new electric furnace is not due to come onstream until 2027 and unions want steelmaking to continue until then. The Guardian understands the talks being offered would focus on future investments. Commenting on the letter, Alun Davies, national officer for Community, the steelworkers’ union, said there were no fresh talks being proposed, and it simply reaffirmed Tata’s position agreed by the unions and Tata at their last meeting in May. He said: “This position is that all unions will seek to conclude the negotiations on a memorandum of understanding and then put this to their members to decide whether it’s good enough.” He added that the letter from Tata confirmed that all discussions would take place through the UK Steel Committee, which is chaired by Community’s general secretary, Roy Rickhuss. Unite warned over the weekend that any closure would be “irreversible” and urged Tata not to “abandon” the workers employed at the plant. It said: “We again call on the company to wait until we have a change of government, not make any irreversible decisions, and enter into meaningful negotiations.” The shadow business secretary, Jonathan Reynolds, was reportedly in talks with the unions and Tata last week in an effort to avert the early closure. The first minister of Wales, Vaughan Gething, and the Welsh economy secretary, Jeremy Miles, said: “The news that Tata could switch off blast furnaces 4 and 5 at Port Talbot next week is extraordinary and will cause huge anxiety for the workforce, their families and the community. “The Welsh government cannot and will not support the closure of both blast furnaces.” Earlier this year, Tata struck a controversial deal with the UK government, securing a £500m grant to build a greener £1.25bn electric arc furnace. However, the company wants to mothball Port Talbot during construction, leaving thousands of local people without work in a town where Tata is the main employer. The Labour party, widely expected to win a majority in Thursday’s general election, has previously promised to invest £3bn in the UK’s steel industry in the next parliament, if elected. This would include the £500m already pledged to Port Talbot. Last month Unite announced that its 1,500 Tata members would commence “all-out indefinite strike action” from 8 July, vowing to continue the strikes until Tata stopped its “disastrous” plan. The Community and GMB unions, which also represent staff at Port Talbot, have said they will wait until after the election before deciding whether to strike. Unite insisted on Saturday it would keep enough staff on site during the strike to ensure all safety procedures would be met, which would ensure the furnaces could function until September. Tata has also now launched a legal challenge against Unite to try to avert its planned strike action, with a decision on whether it has been successful expected on Wednesday. If that is the case, Tata could revert to its plan of closing the second furnace in September. Unite has hit back at the legal action, saying: “Instead of waiting for a likely change of government, Tata has decided to double down, making continued threats and hiring City lawyers to try to stop industrial action on trumped-up technicalities. If they are successful, Unite will reballot. We cannot allow these steel jobs to go.” Tata has previously said it is losing about £1m each day keeping the remaining furnaces open. A Tata spokesperson said: “In the coming days, if we cannot be certain that we are able to continue to safely and stably operate our assets through the period of strike action, we will not have any choice but to pause or stop heavy end operations (including both blast furnaces) on the Port Talbot site. “That is not a decision we would take lightly, and we recognise that it would prove extremely costly and disruptive throughout the supply chain, but the safety of people on or around our sites will always take priority over everything else.”