Indonesia ? Indonesia will not share bird flu samples with the World Health Organization without a legally binding agreement promising the virus won’t be used to develop an expensive commercial vaccine, the health minister said Tuesday.

Siti Fadilah Supari, digging her heels in following a weekslong standoff with the global body, said a letter of guarantee from WHO’s director general Margaret Chan late last month was not good enough.

“We will not share the virus before there is a Material Transfer Agreement,” she told reporters, adding that she hoped one would be drafted during a bird flu meeting in Jakarta in late March between Asia Pacific health leaders and WHO.

Several countries are developing vaccines to protect against H5N1, the bird flu virus strain blamed for 168 human deaths worldwide – more than a third of them in Indonesia.

The virus remains mainly an animal disease, but experts fear it may mutate into a form that easily spreads between humans, potentially killing millions.

Indonesia is worried that large drug companies will use its H5N1 strain, sent to WHO-affiliated laboratories to confirm human infections, to make vaccines that will ultimately be unaffordable for developing nations.