Speaking on Thursday, French President Nicolas Sarkozy warned that a unilateral Israeli military strike on Iran's nuclear facilities would be an "absolute catastrophe".
But he reassured Israel that it was "not alone".
Mr Sarkozy threatened further sanctions against Iran if it failed to respond to US overtures for talks on its nuclear activities.
Mr Obama said the international community would not wait "indefinitely" for Iran to comply with its demands.
The joint declaration said the leaders would "take stock" of whether Iran had complied with demands for a freeze on its nuclear activities at the G20 meeting in Pittsburgh in the US in September.
"Between August and September it's for them to decide how they want things to evolve. Pittsburgh is the date," said Mr Sarkozy