Legislation that would impose the toughest sanctions to date on Iran over its disputed nuclear program has been scheduled for a vote in the House on Wednesday, four days before the inauguration of that country’s newly elected president, a moderate cleric who has made improved relations with the United States an important goal.

The legislation, if enacted into law and fully enforced, could basically eradicate what is left of Iran’s diminished oil exports by coercing its remaining customers to find other suppliers. Proponents of the legislation say that with 376 sponsors, it is expected to pass the House easily. It would then move to the Senate for consideration in September.

But critics say the timing of the House vote has raised sharp questions about the kind of message it would send to Iran’s president-elect, Hassan Rouhani, before he takes office on Sunday. It has also laid bare a divide over Iran policy between Congress and the Obama administration, which has adopted a somewhat less confrontational approach.

Early this month, just weeks after Mr. Rouhani’s victory, the administration received an overture for direct talks with Iran’s leaders, and last week, in what was seen as a modest conciliatory gesture, it moved to ease a sanctions provision concerning sales of medical devices to Iran.