The U.S. House of Representatives easily passed a bill on Wednesday, July 31 to tighten sanctions on Iran, showing a strong message to Tehran over its disputed nuclear program days before President-elect Hassan Rouhani is sworn in, according to Reuters.

The vote also highlighted a growing divide between Congress and the Obama administration on Iran policy ahead of international talks on the nuclear program in coming months. Iran insists the nuclear program is purely for civilian purposes.

The bill, which passed 400 to 20, would cut Iran's oil exports by another 1 million barrels per day over a year, in an attempt to reduce the flow of funds to the nuclear program. It is the first sanctions bill to put a number on exactly how much Iran's oil exports would be cut.

Previous U.S. and EU sanctions have reduced Iran's oil exports by more than half. The United States has worked with Iran's top oil consumers including China, Japan and South Korea to push them toward alternative suppliers of crude.

The bill still has to be passed in the Senate and signed by President Barack Obama before becoming law. The Senate Banking Committee is expected to introduce a similar measure in September, though it is uncertain whether the language to cut exports by 1 million barrels a day will survive.