"The fact that I support this bill as a whole does not mean I agree with everything in it," Obama said in a statement, citing limits on transferring detainees from the US base at Guantanamo Bay, Cuba, and requirements he notify Congress before sharing some defense missile information with Russia as problematic.

The bill, approved by Congress last week, aims with its Iran sanctions to reduce Tehran's oil revenues but gives the US president powers to waive penalties as required. Senior US officials said Washington was engaging with its foreign partners to ensure the sanctions can work without harming global energy markets, and stressed the US strategy for engaging with Iran was unchanged by the bill.