British Steel is desperately trying to secure a government loan to avoid entering administration today (Tuesday).
The UK's second largest steelmaker was seeking £75 million, but has reduced its request to £30m. If it cannot secure the backing, around 25,000 jobs would be put at risk.
If talks do not end in a positive agreement, it is understood administrators will be appointed on Wednesday.
British Steel received a £100m loan from the government to allow it to pay its EU carbon bill and avoid a hefty fine.
The company's owners, Greybull Capital, have consistently blamed "Brexit related issues" for its problems, while the ongoing trade war between the US and China is also having an affect.
On Monday, the government, trade unions and workers all signed a charter designed to encourage big businesses to buy British steel in a bid to help secure the industry's future.
GMB national officer Ross Murdoch said: "Given this latest speculation, these are understandably extremely difficult times for our members."
"Yesterday the government, alongside trade unions and employers, signed a UK Steel Charter at Westminster. They must now put their money where their mouth is.
"GMB calls on the government and Greybull to redouble efforts to save this proud steelworks and the highly skilled jobs."