Pakistan has begun a national polio vaccination programme, but about a quarter of a million children in tribal areas will not take part because of a ban imposed by the Taliban.
The Taliban recently banned vaccinations in North and South Waziristan until the United States ended drone strikes in the region.
The BBC reports officials managed to get into the Waziristan tribal area to provide vaccinations in June, but say they are not optimistic they will be able to carry out vaccinations in this latest round.
Pakistan is one of only three countries where polio is still endemic. Nearly 200 children there were paralysed by polio in 2011 - the worst figures in more than a decade, according to the Lancet medical journal.