Scotland's First Minister Alex Salmond said: "This news is a tremendous fillip for the workforce and the whole Grangemouth community, following what could have been a potential disaster.
"It's been a great team effort from all concerned, including the unions and workforce, the management, Governments - and BP, who have made a material contribution to help defend and secure Scottish jobs and livelihoods.
"I am delighted that people have rallied round to protect these jobs, and now we can all agree that Grangemouth has an outstanding future."
The owner of the Grangemouth plant is expected to announce whether it will reverse a shock decision to close the site, safeguarding hundreds of jobs.
Ineos has been discussing a change in position by the Unite union whose members now say they will commit to a plan aimed at securing its future.
The petrochemicals plant and adjoining oil refinery making up Scotland's largest industrial complex was shut down last week in advance of a planned walkout over pay and conditions.
Ineos did not restart the site after Unite called off the strike but wrote to staff asking them to sign up to changes such as a pay freeze and the closure of the final salary pension.
The company insisted on Wednesday it had no alternative but to close the plant after it failed to persuade its staff to accept the survival plan but Unite general secretary Len McCluskey said yesterday the union would embrace it "warts and all".
Scotland's First Minister Alex Salmond has begun talks with the Unite union over how to save 800 jobs at the Grangemouth petrochemical factory, which its owners plan to close.
Mr Salmond is negotiating with Unite General secretary Len McCluskey and Unite's Scottish secretary Pat Rafferty. Mr McCluskey said earlier the union had decided to embrace a survival plan for the plant "warts and all".