International public health officials signalled Tuesday they are playing for time on the thorny questions of how much swine flu vaccine to make and then whether to use it.

Officials of the World Health Organization and the U.S. Centers for Disease Control acknowledged they hope to put off for as long as possible these difficult decisions, made more challenging by the mildness of the H1N1 swine flu virus.

The WHO’s top flu expert said he doesn’t expect the Geneva-based agency to make any recommendations on whether manufacturers should go into widescale production until early summer.

And the director of the CDC’s national centre of immunization and respiratory diseases said the U.S. may not take a decision on who to vaccinate until late summer or early fall.

“It is going to be a very difficult and complicated discussion if the situation remains as it does at the time when decisions have to be made,” admitted Dr. Keiji Fukuda, the WHO’s acting assistant director general of health security and environment.