DUBAI, United Arab Emirates — Iran’s supreme leader on Wednesday dismissed initial offers at talks in Vienna to save Tehran’s tattered nuclear deal as “not worth looking at,” attempting to pressure world powers after an attack on the country’s main nuclear enrichment site. The comments by Ayatollah Ali Khamenei, who has final say on all matters of state in the Islamic Republic, came after a day that saw Iran’s president similarly ratchet up pressure over the accord.