Fallout from the Sept. 14 attacks is still reverberating as world leaders gather for their annual meeting at the U.N. General Assembly.

Britain, France and Germany, however, joined the United States on Monday in blaming Iran for attacks on key oil facilities in Saudi Arabia, but the Iranian foreign minister pointed to claims of responsibility by Yemeni rebels and said: “If Iran were behind this attack, nothing would have been left of this refinery.”

International experts are, at Saudi Arabia’s request, thoroughly investigating what happened and who was responsible.

The leaders of the U.K., France and Germany — who remain parties to the 2015 Iran nuclear deal — said in a statement that “there is no other plausible explanation” than that “Iran bears responsibility for this attack.”

British Prime Minister Boris Johnson said late Sunday while flying to New York that the U.K. is now “attributing responsibility with a very high degree of probability to Iran” for the attacks by drones and cruise missiles on the world’s largest oil processor and an oil field. He said the U.K. would consider taking part in a U.S.-led military effort to bolster Saudi Arabia’s defenses.