Ballymena-based Wrightbus has yet to comment on media reports that it is set for an order worth £60m for an additional 195 Routemaster buses.
It is understood that London Mayor Boris Johnson got the green light on financing the deal at a board meeting of Transport for London (TfL) on Wednesday.
There had been claims that TfL had been told that without any further order, Wrightbus would close down its Routemaster production line next month.
Wrightbus employs around1,600 people, mainly at its Galgorm factory. TfL has previously bought 805 updated versions of the iconic red bus, after awarding Wrightbus the contract in 2009 to supply up to 1,000 vehicles.
Mr Johnson, who is stepping down, has envisaged 2,000 Routemasters on the city’s streets by 2020.
But Labour’s mayoral candidate Sadiq Khan has vowed to freeze future purchases “of the most expensive buses in the world”.
They cost about £350,000 each.
Any new order would include adjustments to design, including opening windows and a better performing battery.