The WHO accepts that not enough vaccines can be produced for everyone
The World Health Organization has urged pharmaceutical companies to reserve part of their swine flu vaccines for poor countries.
The UN body is asking firms to donate at least 10% of production or to offer reduced prices for poor countries, which may lose out if demand soars.
Six out of 30 leading vaccine producers who met UN chief Ban Ki-moon in Geneva agreed to donate 10%.
Mr Ban said that the world must remain vigilant over the H1N1 virus.
"We may be in a grace period with H1N1 but we are still in the danger zone," he told reporters.
The WHO has confirmed nearly 10,000 swine flu cases in 40 countries.
The new virus is known to have killed 79 people, the vast majority of them in Mexico, where it was first reported.
Health ministers from around the world are in Geneva for the WHO's annual assembly, where they are discussing how to tackle the outbreak.
In other developments:
• Japan asked more than 4,000 schools and nurseries in the Osaka area to shut following an outbreak there
• Inmates at a Mexico City prison reportedly rioted over restrictions on visits because of swine flu
• A 44-year-old man diagnosed with H1N1 died in hospital in Missouri
Dr Margaret Chan, the WHO's director-general, said she had received "very serious commitments" when she met the pharmaceutical companies' representatives in Geneva.
Mr Ban said it was essential for vaccine-producers to work with governments in order to avert the worst potential impact of H1N1.
"Partnerships with the private sector are absolutely vital," he said.
Global solidarity in confronting the virus, he said, "must mean that all have access to drugs and vaccines".
Correspondents say the impact of a pandemic, or global epidemic, is expected to be worse in poor countries, where people with other illnesses such as Aids and malaria are more susceptible to swine flu, and national health systems are less able to cope.
Manufacturers will not be able to start making the vaccine until mid-July at the earliest, weeks later than previous predictions, experts told the WHO.
It will then take months to produce the vaccine in large quantities.
The WHO accepts that it would be impossible to produce enough vaccine for all 6.8 billion people on the planet.
Mass production of swine flu vaccines could also affect the manufacture of seasonal flu vaccines.