“Iran’s ability to impact the U.S. will probably be mostly within the Middle East theater,” said Neil Beveridge, a senior analyst at Bernstein, a market research firm. “Iraq and Saudi Arabia are obvious targets.”

Tensions in the Strait of Hormuz

Tankers carrying most of the oil leaving the Persian Gulf region — about 18 million barrels a day — as well as giant vessels loaded with liquefied natural gas, must pass through the Strait of Hormuz, a narrow channel that separates the United Arab Emirates, Oman and Iran and leads to the Indian Ocean.

The strait is 21 miles wide at its narrowest point, and the width of the shipping lane in either direction is just two miles wide, according to the United States Energy Information Administration.

Iran’s coastline covers much of the east side of the gulf, leaving Tehran well placed to harass shipping with small boats, missiles, mines and other weapons. Last year, Iran seized a number of tankers in the area in an apparent effort to show that if Tehran was not permitted to export its oil, then supplies from other producers in the area were at risk.

Market participants worry that Iran could step up such attacks on shipping, although such a move would be likely to bring a quick response from United States military forces in the area.

Other vulnerable points

Iran has other options for retaliating against Washington and its allies. It was clear in September that key Saudi oil installations could be knocked out with missile and drone attacks. Analysts worry about a similar strike by Iran, or a larger version.

Analysts also say the oil installations of Saudi Aramco and other producers around the Persian Gulf could prove vulnerable to cyberattacks that might severely disrupt their operations.