The U.N. Children's Fund said health workers in Iraq will begin immunizing more than four million children against polio next week. This will be followed in early March by a measles campaign.

UNICEF does not explicitly link the immunization campaigns to the possibility of war in Iraq. But it acknowledges that efforts to protect Iraq's children from polio and measles are occurring in the shadow of ongoing international debate over a potential conflict in Iraq.

UNICEF spokeswoman Wivina Belmonte said time is of the essence. Beginning on February 23, she said, more than 14,000 health workers will fan out across various parts of Iraq, going door to door to make sure every child under five has been immunized against polio.

She said Iraq had a major outbreak of polio in 1999, but for the past three years, no cases have been reported. "What is important, as you well know, is that polio has no passport. It is easy, if people are on the move, it is easy for that to go from one place to another and spread, and that is the concern. So, the emphasis on the polio campaign is to make sure that it does not flare up again," Ms. Belmonte said.

The U.N. Refugee Agency estimates between 600,000 and 1.5 million people could flee to neighboring Iran, Turkey, Jordan and Syria should war break out in Iraq. UNICEF said the polio campaign is crucial to protecting Iraqi children from this crippling disease and to prevent polio outbreaks elsewhere in the region.

Also termed crucial is the campaign to track down children who were missed during earlier measles vaccination campaigns. UNICEF's Wivina Belmonte said close to 500,000 Iraqi children under five have not been vaccinated against measles.

"We know this is a huge challenge for us because it is not just the under fives that we need to make sure to reach, but we also need to reach children between the ages of six and 12. Many of them were not vaccinated against measles in the mid-'90s when vaccines were in short supply. If children and families are on the move, measles is something else that spreads very quickly and is fatal for kids," she said.

UNICEF said Iraqi children are extremely vulnerable. The agency estimates that one out of eight Iraqi children dies before the age of five, one of the worst rates in the world. It says one-third of Iraqi children are malnourished and one-quarter do not have access to safe water.