The U.S. push to reduce Iranian oil exports to zero will tighten crude markets significantly in the short term, but is unlikely to have a big effect on prices over a longer period, Barclays said in a note.

Washington this week demanded that buyers of Iranian oil stop purchases by May 1 or face sanctions.

“The announcement implies material upside risk to our current $70 per barrel average price forecast for Brent this year, compared with the year-to-date average of $65 per barrel. But (it) does not affect our view on longer-term prices materially,” Barclays said.

Barclays also said that the U.S. move increased the risk of conflict in the Middle East, including the potential closure of the strategic Strait of Hormuz.