Updated

Some 21 nations in the Middle East and nearby regions have jointly made the eradication of polio an emergency priority and recognized that Pakistan is a key part of the problem, the World Health Organization said Wednesday.

The joint resolution by nations who are part of the U.N. health agency's Eastern Mediterranean region have called on Pakistan to urgently vaccinate all of its children to prevent the virus from spreading internationally.

Pakistan also approved the resolution, which the Geneva-based agency says includes Afghanistan, Bahrain, Djibouti, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Qatar, Saudi Arabia, Somalia, Sudan, Syria, Tunisia, the United Arab Emirates, and Yemen.

The problem is particularly challenging in Pakistan, where a U.N.-backed eradication campaign has suffered from violence and mistrust directed against polio workers and people who want their children vaccinated.

Earlier this week, WHO officials said the polio virus has now been confirmed in 13 of 22 children who became paralyzed in a northern Syrian province. The health agency said the Syria outbreak comes from a strain that originated in Pakistan, where, along with Afghanistan and Nigeria, it is endemic - and has been spreading across the Middle East.

It said the virus has been detected in Egypt, and closely related strains of Pakistani origin turned up in sewage samples in Israel, the West Bank and Gaza Strip, but higher immunization rates in those places have helped keep the virus in check.

A third of the nations in the WHO's Eastern Mediterranean region are conducting mass polio vaccination programs, the agency said, and more such campaigns are planned for December.

The nations in those regions also said they are trying to improve access for health workers to reach children who have not yet been vaccinated. WHO said its emergency "outbreak response" to polio in Syria and the region is expected to continue at least six to eight months more.

In Syria, WHO and UNICEF, the U.N. children's agency, are trying to work with other humanitarian agencies to reach more of the millions of people affected by the civil war including unvaccinated children.

The two agencies "are coordinating the vaccination campaign with all concerned parties to make sure that all children are vaccinated no what where they are located," said Dr. Jaouad Mahjour, head of communicable diseases prevention and control for WHO's regional office.

Pakistan, which had 198 confirmed polio cases in 2011 - the highest number of any nation in the world that year - cut that number down to 58 in 2012 through an aggressive vaccination program.

But the program has been marred by violence carried out by militants who oppose the U.N. and government-led vaccinations, claiming it is meant to sterilize Muslim children.

In October, in a village outside the provincial capital of Peshawar, a bomb explosion killed a police officer and a member of a volunteer peace committee when it went off next to van carrying Pakistani security guards who were protecting workers carrying out an anti-polio drive in the country's northwest.

In May, Pakistani authorities had to suspend a four-day vaccination program after gunmen shot dead a female polio worker and wounded another.

The militants' suspicions stem from the CIA's use of a Pakistani doctor from an immunization program in the hunt for Osama bin Laden two years ago. The militants also accuse polio workers of spying for the U.S. government, and two Pakistani Taliban militants banned the polio work from two tribal regions due to opposition to U.S. drone strikes.

Those suspicions were reinforced by the disclosure that the CIA also used a Pakistani doctor for a hepatitis vaccination program to try to get blood samples from bin Laden's family before U.S. commandos killed him in May 2011.