The Associated Press reported on Monday that a document it had obtained in Vienna, where the offices of the International Atomic Energy Agency (IAEA) are located, could spark questions about assurances that were made by President Barack Obama and other Western leaders.

It said the document was the only secret text linked to last year’s agreement between Iran and six foreign powers. It said that after a period between 11 to 13 years, Iran could replace its 5,060 inefficient centrifuges with up to 3,500 advanced machines.

Since those are five times as efficient, the time Iran would need to make a weapon would drop from a year to six months, the AP said.

Iran says its enrichment is peaceful and US intelligence agencies have concluded that the country currently has no ambitions to produce a weapon.