VIENNA (AP) — Iran could produce enough weapons-grade uranium to arm a nuclear bomb within two to four months but would still face serious “engineering challenges” — and much longer delays — before it succeeds in making the other components needed for a functioning warhead, a respected U.S. think tank said Monday.

While Iran denies any interest in possessing nuclear arms, the international community fears it may turn its peaceful uranium enrichment program toward weapons making — a concern that is growing as Tehran expands the number of machines it uses to enrich its stockpile of enriched uranium. As those fears grow, so does concern that Israel could carry out its threats to attack Iran’s nuclear facilities before that nation reaches the bomb-making threshold.