Strait of Hormuz map shows where US Navy warships will blockade Iran

President Donald Trump is following through on a threatened blockade of Iranian ports by U.S. forces after peace talks broke down between the United States and Iran on April 12.

The blockade started close to 10 a.m. ET April 13. It will affect “vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman,” according to the U.S. Central Command.

At least 15 U.S. warships will be part of the blockade, according to an unidentified official cited by The Wall Street Journal. The U.S. military has not officially released specifics of the blockade, nor has it released information about the number of warships involved and whether warplanes will be used. NATO allies are refusing to join the blockade.

Learn more:What to know about the blockade.

U.S. officials notified shipping companies that the blockade will apply to all vessel traffic, regardless of the country flag they fly, Reuters reported.

In Israel, Prime Minister Benjamin Netanyahu said he supported the blockade and vowed to continue fighting in Lebanon ahead of peace talks in Washington over that conflict.

Where the Iranian ports are

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U.S.-Iranian peace talks in Pakistan broke down as each country blamed the other for the impasse. It was unclear how the failed talks and U.S. blockade would affect the two-week ceasefire in Iran.

Tankers stalled near the Strait of Hormuz

In early April 2026, hundreds of tanker ships, in clusters, awaiting entry into the Strait of Hormuz.

How does a naval blockade work?

A blockade has to be announced and its boundaries defined. This allows neutral shipping vessels to take alternate routes or ask for passage on humanitarian grounds.

Naval and air forces conduct surveillance of the region. They monitor ships approaching the area and watch for ships with suspicious flags or cargo.

Ships are tracked using:

• Shipping transponder data, or Automatic Identification System transmissions
• Radar
• Aircraft patrols
• Intelligence reporting
• Coordination with partner nations
• Commercial maritime data

U.S. forces will be monitoring an area about 21,000 square miles in size along the Iranian coastline − a space roughly 87% the size of West Virginia − according to a calculation by USA TODAY, based on a 12 nautical mile stretch of territorial water.

What happens when a warship intercepts a ship?

Steps of a naval blockade, according to the Commander's Handbook on the Law of Naval Operations, include:

• Warning is issued: The warship identifies itself. The suspect ship is contacted and told it’s approaching a blockaded area. It's ordered to halt.
• Ship is boarded: The warship sends a boat with one officer or more to the ship for a visit and search. The officers and boat crew are armed at the discretion of the warship’s commander. If a search at sea isn’t practical, the ship is directed to a neutral area.
• Papers are checked: A ship’s crew members are asked for details of the vessel's voyage, cargo, flag and route. The crew may be questioned.
• Ship may be boarded and searched: If “reasonable grounds” exist the ship is violating the blockade, it may be captured. If it resists capture, it may be attacked.
• Ship is detained, rerouted or released: The ship may be diverted, detained, captured or released depending on what’s found and the applicable authority.

If Iran's ports are threatened, then no ports in the Persian Gulf or Gulf of Oman would remain secure, according to a statement from Ebrahim Zolfaghari, an Iranian military spokesperson. He said any blockade of vessels in international waters would amount to "piracy," Iranian state media reported.

How the Iran blockade will affect oil and gas prices

Oil prices rose above $100 a barrel after Trump announced the blockade.

CONTRIBUTING Christopher Cann, Thao Nguyen and Kathryn Palmer

SOURCE USA TODAY Network reporting and research, Reuters; U.S. Navy; U.S. Coast Guard; U.S. Naval Institute; International Committee of the Red Cross