The White House has begun to take steps if Iran is unwilling to "pursue its responsibilities" on the nuclear issue, spokesman Robert Gibbs said on Tuesday.
"We've begun to take those steps, if Iran is unwilling to pursue its responsibilities," Gibbs said.
President Mahmoud Ahmadinejad on Tuesday dismissed a looming deadline from the Obama administration and its allies for Tehran to accept a UN-drafted deal to swap enriched uranium for nuclear fuel.
President Barack Obama wants Iran to respond to an offer of dialogue and show it will allay fears of weapons development. Otherwise, Washington and its allies are warning of new, tougher sanctions on Iran.
Gibbs said Ahmadinejad may not recognize the deadline but "it is a very real deadline for the international community."
AP and Reuters contributed to the report