The prime minister promised the extra places last week
The government says there will be 10,000 more university places in England this autumn, mainly in maths, science, technology and engineering.
The extra places will be allocated by the higher education funding council in consultation with universities.
They will be part-funded: universities will get students' tuition fees but not grants for teaching and other support.
Funding is from existing budgets and in part by cutting student loan repayment holidays from five years to two.
The repayment holidays were announced last year, to take effect from 2012.
The idea was to help graduates buying a home or starting a family - but the government has now decided the extra places in a recession are a greater priority.
Similarly, strategic thinking lies behind the decision to confine the additional numbers to the "New Industry, New Jobs agenda", such as the so-called Stem subjects, and only for full-time undergraduates.
NORMAL FUNDING PER PLACE (2008-09)
Some subjects need more resources than others
Group A: £15,856 - clinical stages of medicine and dentistry courses and veterinary science
Group B: £6,739 - lab-based science, pre-clinical medicine and dentistry, engineering and technology
Group C: £5,153 - subjects with a studio, lab or fieldwork element
Group D: £3,964 - base price, for all other subjects
Plus: tuition fee from student: £3,145
Latest application figures from the admissions service Ucas showed more people wanting to study the subjects affected by the announcement, apart from chemistry.
There has been a 10.8% rise in the numbers wanting to take mathematics degrees, for example, and 19.1% more applying to study mechanical engineering. Chemistry numbers were down 1.1%.
The move comes as demand for university places continues to rise, with 10% more applicants this year than last across the UK - about 50,000 people.
Prior to the latest announcement only 3,000 more full-time places were being provided - suggesting tens of thousands would not get on a course.
Announcing the details, Business Secretary Lord Mandelson said: "By making available 10,000 extra places in science, technology and maths we are not only helping more individuals with the ambition and ability to go to university but also investing in this country's future.
"Our expansion of higher education is more important now than ever as we continue to invest in a highly skilled workforce to win the jobs of the future and lead the way in building Britain's future."
The funding the government says it is providing will cover students' maintenance grants, for those who get them, and their loans for tuition fees.
A spokesman for the Higher Education Funding Council for England (Hefce) said it had yet to receive guidance from the Business, Innovation and Skills department (Bis) on how the extra places would be shared out. This was expected soon.
Hefce's normal funding for these places can be many thousands of pounds more than just the tuition fee, depending on the course - leaving universities with potentially big shortfalls.
Base funding for example is £3,964 plus the £3,145 tuition fee (2008-09 prices). For the most expensive courses, involving the clinical stages of medicine and dentistry, and veterinary science, funding is £15,856 per place on top of the tuition fee.
A statement from Bis said higher education institutions had said they could recruit more students "without compromising the quality of their offer".
The 1994 Group of 18 research-intensive universities said they would want to help meet the extra demand - but said additional teaching funding was also required "to maintain the quality of student experience".
"Offering the highest quality of degrees is crucial to give graduates the best chances of employability in a tough job market," said the group's chair-elect, Professor Paul Wellings, vice-chancellor of Lancaster University.
"In this environment, we must ensure that UK universities stay focused on the quality of their degrees."
The message was echoed by another elite organisation, the Russell Group, which said any growth must be funded in a sustainable way that would not create real and long-term difficulties and undermine the quality of the student experience.
National Union of Students vice-president Aaron Porter said thousands wanting to study non-Stem subjects would still be without a place.
"We understand the current pressures on public finances, but the government must also make the right long-term decisions.
"It is surely better to bear the cost of additional university places now than to shoulder the burden of long-term unemployment later."
The shadow secretary for universities and skills, David Willetts, said the government's "belated U-turn" was welcome.
"But we are not out of the woods yet.
"Around 40,000 more applicants are likely to be rejected this year than last. And there is nothing for those whose A-levels stop them from applying for Stem courses."