LONDON (Reuters) - Iran has extended the range of its land-to-sea ballistic missiles to 700 km (435 miles), a senior Iranian military official said on Tuesday amid rising tensions with the United States over Tehran’s missile program.

U.S. President Donald Trump pulled out of an international agreement on Iran’s nuclear program in May and reimposed sanctions on Tehran, saying the deal was flawed because it did not include curbs on Iran’s development of ballistic missiles or its support for proxies in Syria, Yemen, Lebanon and Iraq.

Iran, which says its missile program is purely defensive, has threatened to disrupt oil shipments through the Strait of Hormuz in the Gulf if the United States tries to strangle Iranian oil exports.

“We have managed to make land-to-sea ballistic, not cruise, missiles that can hit any vessel or ship from 700 km,” Amirali Hajizadeh, head of the Iranian Revolutionary Guards’ air space division, was quoted as saying by Fars news agency.

Hajizadeh said the Guards focused on extending the land-to-sea missile’s range after Iranian Supreme Leader Ayatollah Ali Khamenei asked the military a decade ago about the possibility of “hitting ships” with ballistic projectiles.

He did not give details on the previous range of the missiles. In 2008, Iran displayed a ground-to-sea missile that it said could travel about 290 km (180 miles).

On Monday, the U.S. special envoy on Iran, Brian Hook, said that Tehran’s ballistic missile program was exacerbating tensions in Yemen, Iraq and Syria. “We are accumulating risk of regional conflict if we do not do more to deter Iran’s missile proliferation in the Middle East,” Hook said.

The Islamic Republic’s government has ruled out negotiations with Washington over its military capabilities and dismissed U.S. assertions that its activities in the Middle East are destabilizing.

Hajizadeh said some short-range Iranian missiles had been used over the past two years in Syria’s civil war, in which Iranian forces have fought in support of President Bashar al-Assad against rebels and militants.

He also said Iranian drones had carried out 700 attacks on Islamic State militant positions in Syria.

Iran’s Revolutionary Guards have sent weapons and thousands of soldiers to Syria to help shore up Assad during the more than seven-year-long conflict there.