Scotland’s First Minister Alex Salmond is trying to broker a “truce” in the dispute that has led to the Ineos petrol refinery at Grangemouth in Scotland being shut down.

Salmond met representatives of Ineos and the Unite union on Thursday, and afterwards he called for Unite to confirm in writing that it would not strike this year, and at the same time, for Ineos to restart operations and return the site to normal production.

He told the BBC’s Good Morning Scotland programme: “If the plant stays down and we stay in the war of words and the exchange of press releases and exchange of interviews and exchange of tweets then there is the risk things will deteriorate further and the fundamental risk is to the future of the Grangemouth plant.”

Earlier this week the Unite union called off a two-day strike scheduled to commence on Sunday, but Ineos said the site would remain shut down until Unite agreed there would be no more strikes.

On Friday Ineos was reported to be couriering letters to employees with proposals for new pay and pensions which include freezing the basic salary, offering no bonuses until at least the end of 2016, and ending the company’s final salary pension scheme. Unite claimed employees were being told they had to agree to the new arrangements on Monday.

Pat Rafferty, Unite’s Scottish secretary, said the union had offered not to take industrial action up until the end of December at a meeting the two sides had earlier this week at the arbitration service ACAS, on condition that Ineos would drop the Monday deadline and negotiate a settlement.

Ineos Grangemouth (UK) chairman Calum MacLean said that for safety reasons the company could not restart the site until the risk of further industrial action was removed.

He added: “We can confirm that we would restart if there was a clear guarantee that there would be no further action during the next 60 days.

“This would allow us to complete a full consultation process with our employees on the changes that the site so urgently needs.”

The dispute that led to a vote for strike action had centred on the company’s treatment of union official Stephen Deans.