PARIS — Driven by electoral pressures and Germany’s postwar aversion to war and nuclear power, Chancellor Angela Merkel has deeply strained relations with allies in the European Union and the NATO alliance, raising new questions about Germany’s ability to play a global role in foreign policy, even as its economic power and influence grow.

By abstaining in the Security Council on the resolution authorizing military action to protect Libyan civilians — and by refusing on Wednesday to participate in the enforcement of an arms embargo on Libya that the United Nations authorized — Germany pointedly refused to go along with the political aims and leadership of its two most important European allies, Britain and France, as well as the United States. The decision made the idea of a united European foreign policy seem further away than ever, even if France had broken solidarity first by suddenly recognizing the Libyan opposition as the legitimate government of the country.

And by choosing to shut down seven older nuclear plants in Germany after the nuclear crisis in Japan, Mrs. Merkel reversed her own policy and further ruffled relations with France, which derives 75 percent of its electric power from nuclear plants.

The new strains come weeks after Germany issued demands for economic austerity in the countries that use the euro as the price for new loan guarantees to troubled countries like Greece and Ireland. Portugal is thought by many to be next in line for a bailout. Germany, the richest and largest member of the European Union, has been tough and not always diplomatic in refusing to come to the aid of more profligate countries unless they undergo painful budget cuts and economic restructuring.