Cuba was plunged into darkness for the second time in less than a week on Saturday after its national power grid failed again, strained by aging infrastructure and a US oil blockade. The blackout comes as Havana said it is open to “a serious and responsible dialogue” with the United States. Cuba, under a US blockade since 1962, has faced repeated fuel crises, said Helen Yaffe, professor of Latin American political economy at the University of Glasgow. She noted that renewable energy now helps meet daytime demand, with solar power covering nearly half of needs, but the country still lacks storage capacity and fuel for transport. "How long can any nation survive without oil?" she asked.