US President Barack Obama said on Friday that it would take time for Iran to rejoin the global economy, as the country's leadership and citizens express unease that a sanctions windfall has been slow to materialize.

"It will take time for Iran to reintegrate into the global economy, but Iran is already beginning to see the benefit of this deal," Obama said at a meeting of world powers in Washington.

The international community lifted a raft of sanctions on Iran in exchange for the country curbing its controversial nuclear program.