It is understood shipbuilding at Portsmouth will stop.
The company may cut more than 1,000 jobs in total between Portsmouth and the Govan and Scotstoun yards in Glasgow.
It is thought Govan will not close. An announcement had originally been expected on Thursday.
The job losses are expected to result from a reduction in work following the completion of two Royal Navy aircraft carriers.
The BBC's political editor Nick Robinson said: “I understand the announcement on job cuts at BAE's shipbuilding yards is likely to be brought forward to this morning.”
It is thought staff will be told at 10:00 with an official announcement at 11:00.
Repairs and maintenance work could continue at Portsmouth, although no new ships would be built there.
The defence secretary will make a statement in the Commons if the announcement is made.
Union leaders have said they will hold talks with BAE Systems early next week.
Some of the jobs being lost may be offset by a contract to build the new Type 26 Global Combat Ship.
But BAE Systems has yet to announce which of its UK shipyards will be chosen to carry out the work.
A well-placed source has told the BBC the government was “acutely conscious of the politics of the Clyde” ahead of next year's referendum on Scottish independence.
The leader of Portsmouth council, Gerald Vernon-Jackson, questioned why a decision was being taken before the referendum.
He told the BBC's Today programme: “Portsmouth is the last place in England that has the ability to build advanced warships for the Royal Navy and I'm very concerned that with a potential independence vote in Scotland, if Portsmouth shipbuilding is shut down, what would remain of the UK would have no ability to build advanced warships.
“We're an island nation. We depend on sea trade for the food we eat, for the fuel in our cars, for the gas in our central heating systems, and the Royal Navy has never brought ships from abroad.
“It would just mean either that that would have to change and the Royal Navy would have to buy ships from France or Germany – or we'd have to spend a huge amount of public money re-employing people, re-skilling people here in Portsmouth”.
Portsmouth South's Liberal Democrat MP Mike Hancock said workers would be “devastated” by the development.
He said: “Everyone going into the yard today are going in there unknowing whether they have a future or not. That is a personal tragedy for them and a catastrophe for the city of Portsmouth to lose so many highly skilled jobs which will be virtually impossible to replace in that line.
“I think it is a national disgrace that we are going to put all their expertise and investment that has gone into the yard in Portsmouth at risk by closing it down, putting all of your eggs into one basket.
“If this government has learned anything it should have learned that will have been a grave error of judgement.”
But the Scottish secretary of the GMB union, Harry Donaldson, said any decision should be based on economic rather than political grounds.
Speaking on BBC Breakfast, he said: “To be perfectly frank I think it is disgraceful that politicians are getting into looking at these yards as a political football.
“It needs to be about communities, it needs to be about people and it needs to be about what is best for Scotland and the rest of the UK as a maritime nation.”
The leader of Scottish Labour, Johann Lamont, said there was “uncertainty” because of the forthcoming referendum.
But Ms Lamont, whose Holyrood constituency includes the Govan yard, added: “
It emerged on Monday that the UK government was planning to announce that it will need to spend an extra £800m on the carriers, taking the total costs to more than £6bn – double the original estimate.
Beyond the carriers there are currently no new orders on the books of BAE's Glasgow yards at Govan and Scotstoun.
Any job losses, however, may not take effect immediately because some work on the aircraft carriers is planned until 2015.
The Confederation of Shipbuilding and Engineering Unions said it would hold talks with senior BAE Systems executives early next week to “examine the business case” of the forthcoming announcement on jobs.
There are currently 3,200 people employed by BAE across Govan and Scotstoun, and 1,200 employed in shipbuilding at Portsmouth.
BAE launched a review of its defence work 18 months ago.
A BAE spokeswoman said on Tuesday: “We continue to work closely with the Ministry of Defence to explore all possible options to determine how best to sustain the capability to deliver complex warships in the UK in the future.
The Scottish government said it has been in dialogue for some time with BAE Systems over the future of the Clyde shipyards.