Hard-liners are set to tighten control of Iran this week in a parliamentary election stacked in their favor, as the leadership closes ranks in a deepening confrontation with Washington.

Big gains by security hawks would confirm the political demise of the country's pragmatist politicians, weakened by Washington's decision to quit a 2015 nuclear deal and reimpose sanctions in a move that stifled rapprochement with the West.

More hard-liner seats in Friday's vote may also hand them another prize — more leeway to campaign for the 2021 contest for president, a job with wide day-to-day control of government.