Greater Manchester leaders have been given a deadline of midday to reach a deal with the government over moving to tier three Covid restrictions.
If an agreement is not reached, Communities Secretary Robert Jenrick said he would advise the PM, who would decide on the next steps.
In this situation, the BBC's Laura Kuenssberg said the "implication" was the top tier of rules would be imposed.
Local leaders want more financial support before agreeing to the move.
The government and local leaders - including mayors and MPs - have been embroiled in ten days of talks over tighter rules for Greater Manchester's 2.8m population.
The "very high" alert level, also known as tier three, would mean closing pubs and bars which do not serve meals, and additional restrictions on households mixing.
Mr Jenrick said local leaders had been "so far unwilling to take the action that is required to get this situation under control".