Just in case it hasn't been mentioned before, this will resolve the dependencies automatically:background:
By default the backports repository has a lower pinning priority than the regular stable repository so apt will try to resolve any dependencies from the stable repository, even if there is a newer version in backports. Only if there's no package with the required name at all in the stable repository the backports repository will be used. In this case that means that regardless of the insufficient version number ure will be taken from the stable repository because it exists there.
-t (target) changes that behavior by giving the specified repository the highest pinning priority for this one command. Thus -t squeeze-backports means: Resolve any dependencies by using the squeeze-backports repository if possible, fetch the rest from whatever repository among all the others has the highest pinning priority.
In our case this means ure (and any other dependency that exists in the backports) will be installed from squeeze-backports. Therefore -t squeeze-backports SHOULD be used whenever you explicitely want to install anything from backports.