The US says it wants to create an international military coalition to safeguard waters around Iran and Yemen.
Marine Gen Joseph Dunford, chairman of the US Joint Chiefs of Staff, said he wanted to "ensure freedom of navigation" in the region, which provides essential trade routes.
The US has blamed Iran for attacks on oil tankers in May and June.
Gen Dunford said the US was talking to a number of countries with the "political will" to support the plans.
The US would provide "command and control" ships, leading surveillance efforts, he said. However, the aim would be for other countries to offer boats to establish patrols nearby, and escort commercial ships carrying their flags through the area.
Gen Dunford said the US would "work directly with the militaries to identify the specific capabilities" each country has to support the initiative.
The Straits of Hormuz and Bab al-Mandab are essential strategic marine locations, providing access from the ocean into the Gulf and the Red Sea.
The general said the size of the initiative depended on the number of countries which decided to take part.
"With a small number of contributors, we can have a small mission," he said. "We'll expand that as the number of nations that are willing to participate identify themselves."
Everyday, nearly four million barrels of oil pass through Bab-al Mandab to the rest of the world.