Iran could shut the Strait of Hormuz as a way of hitting back against its enemies, a senior Iranian lawmaker said on Thursday, with a second member of parliament indicating Tehran would seal off the vital waterway if the US joined Israel’s military strikes against the Islamic Republic.

Iran has in the past threatened to close the Strait of Hormuz to traffic in retaliation for Western pressure, and shipping sources said on Wednesday that commercial ships were avoiding Iran’s waters around the strait.

“Iran has numerous options to respond to its enemies and uses such options based on what the situation is,” said Behnam Saeedi, a member of the Iranian parliament’s National Security Committee presidium, according to the semi-official Mehr news agency.

“Closing the Strait of Hormuz is one of the potential options for Iran,” he added.

The Strait of Hormuz lies between Oman and Iran and is the primary export route for Gulf producers such as Saudi Arabia, the United Arab Emirates, Iraq and Kuwait.

About 20 percent of the world’s daily oil consumption — around 18 million barrels — passes through the Strait of Hormuz, which is only about 33 kilometers (21 miles) wide at its narrowest point.

Iranian lawmaker Ali Yazdikhah said Tehran would continue to allow free shipping in the Strait and in the Gulf, so long as Iran’s vital national interests were not at risk, according to the Mehr news agency.

“If the United States officially and operationally enters the war in support of the Zionists [Israel], it is the legitimate right of Iran in view of pressuring the US and Western countries to disrupt their oil trade’s ease of transit,” Yazdikhah said.

Tehran has so far refrained from closing the Strait because all regional states and many other countries benefit from it, Yazdikhah added.

“It is better than no country supports Israel to confront Iran. Iran’s enemies know well that we have tens of ways to make the Strait of Hormuz unsafe and this option is feasible for us,” the parliamentarian said.

US President Donald Trump is keeping the world guessing about whether the United States will join Israel’s strikes on Iran, which began last week.

Israel says its sweeping assault on Iran’s top military leaders, nuclear scientists, uranium enrichment sites, and ballistic missile program is necessary to prevent the Islamic Republic from realizing its avowed plan to destroy the Jewish state.

Iran has retaliated by launching over 450 missiles and around 1,000 drones at Israel. So far, 24 people have been killed in Israel and more than 500 wounded.