Stock futures were lower ahead of Friday’s session, with investors monitoring conflict in the Middle East between Iran and Israel, and potential direct U.S. involvement.

Futures tied to the Dow Jones Industrial Average slipped 221 points, or 0.5%. Nasdaq 100 futures ticked down 0.6%%, while S&P 500 futures fell 0.4%. Regular trading was closed in the U.S. on Thursday for the Juneteenth holiday.

Investors remain jittery as the conflict between Israel and Iran has yet to cool. President Donald Trump is weighing direct U.S. involvement with a strike on Tehran, with the White House on Thursday saying that he will make a final decision within the next two weeks. Trump previously called for Tehran’s complete surrender, to which Iran’s supreme leader, Ayatollah Ali Khamenei, labeled the notion “threatening and ridiculous.”

International benchmark Brent

as well U.S. crude oil