There are now 10,243 people who have been infected with swine flu as confirmed by laboratories, said Fadela Chaib, a spokeswoman for the World Health Organization. She said there have been 80 deaths, mostly in Mexico.
The 413 newly confirmed cases come mostly from the United States and Japan, Chaib said.
The continued spread of the disease comes as the WHO's 193 member states are meeting in Geneva to hammer out plans for treatments, pandemic response and eventually vaccinations to combat the disease as much as possible. The global health body has its pandemic alert scale at phase 5, meaning a global flu epidemic is deemed "imminent."
WHO on Tuesday urged drug makers to reserve for poor countries a portion of any pandemic swine flu vaccine they develop, but received few concrete offers as experts disclosed that an effective flu shot was still months away.
The health agency wants companies to donate at least 10 percent of their production or offer reduced prices for developing nations that could otherwise be left without vaccines if there is a sudden surge in demand. Some drug companies were skeptical about what such a commitment would mean for business.
"I don't think that all of the answers are there yet," said Eric Althoff, a spokesman for Swiss pharmaceutical giant Novartis AG.
U.N. Secretary-General Ban Ki-moon met with 30 major pharmaceutical manufacturers and said solidarity - meaning "that all have access to drugs and vaccines" - was needed.
The only major drug maker that publicly agreed to the WHO request Tuesday was Britain's GlaxoSmithKline PLC, which said it would donate 50 million doses in a pandemic and offer more that WHO could buy at a discount for poor countries.
A second drug maker with only limited production capacity said it would share half of its vaccine doses. WHO officials declined to identify the company because the deal has yet to be signed.
The impact of a pandemic is expected to be worse in poor countries, where people with other diseases such as AIDS and malaria are more susceptible to swine flu and national health systems are less able to respond.
Many rich countries - including Britain, Canada, Denmark, France and Switzerland - have already signed deals with vaccine makers that promise them millions of pandemic vaccines as soon as they're available.
"This flu will continue to spread across the United States," acting director of the U.S. Centers for Disease Control and Prevention Richard Besser told CBS' The Early Show on Tuesday.
Manufacturers won't be able to start making the vaccine until mid-July at the earliest, weeks later than previous predictions, according to an expert panel convened by WHO. It will then take months to produce the vaccine in large quantities.
They estimated that under the best conditions, drug companies could produce nearly 5 billion doses of swine flu vaccine in the year after beginning full-scale production.