to be in a situation where it is very difficult to decide what to do, usually because both of your two choices of action would cause problems

UN troops are in a cleft stick: something has to be done for the civilian population, yet to retaliate would surely be the spark to ignite all-out war. 联合国军队进退两难：为了平民不得不采取行动，可是还击势必会引发全面战争。