HOUSTON — If Iran were to follow through with its threat to blockade the Strait of Hormuz, a vital transit route for almost one-fifth of the oil traded globally, the impact would be immediate: Energy analysts say the price of oil would start to soar and could rise 50 percent or more within days.

An Iranian blockade by means of mining, airstrikes or sabotage is logistically well within Tehran’s military capabilities. But despite rising tensions with the West, including a tentative ban on European imports of Iranian oil announced Wednesday, Iran is unlikely to take such hostile action, according to most Middle East political experts.

United States officials say the Navy’s Fifth Fleet, based in nearby Bahrain, stands ready to defend the shipping route and, if necessary, retaliate militarily against Iran.

Iran’s own shaky economy relies on exporting at least two million barrels of oil a day through the strait, which is the only sea route from the Persian Gulf and “the world’s most important oil choke point,” according to Energy Department analysts.