Iran’s foreign minister said Thursday that sanctions imposed by the Trump administration are “unacceptable,” but his country is committed to an international nuclear deal that has steadily unravelled amid rising tensions.

On a visit to Tokyo, Mohammad Zarif defended Iran’s right to respond to the U.S. pullout from the nuclear deal last year and the imposition of sanctions.

“We believe that escalation by the United States is unacceptable and uncalled for. We have exercised maximum restraints,” he said. In other comments carried on the semi-official Mehr news agency, Zarif was quoted as saying “a multilateral deal cannot be treated unilaterally.”

Recent days have brought allegations of sabotage attacks targeting oil tankers off the coast of the United Arab Emirates, a drone attack on a Saudi oil pipeline claimed by Yemen’s Iran-allied Houthi rebels, and the dispatch of U.S. warships and bombers to the region.

Saudi Arabia’s Deputy Defence Minister Khalid bin Salman tweeted Thursday that Tehran had ordered “the terrorist acts” on the pipeline.

“The attack by the Iranian-backed Houthi militias against the two Aramco pumping stations proves that these militias are merely a tool that Iran’s regime uses to implement its expansionist agenda in the region,” he wrote.

Iran has been accused by the U.S. and the UN of supplying ballistic missile technology and arms to the Houthis, which Tehran denies.

Saudis launch airstrikes against Houthis

Saudi Arabia responded to Tuesday’s drone attack with a wave of airstrikes on Houthi targets in Yemen’s rebel-held capital, Sanaa. On Thursday, residents scrambled to pull 14 wounded people from the rubble of a building.

Fawaz Ahmed told The Associated Press he saw three bodies being retrieved from the rubble — a father, mother and child, all buried together. Yemen’s Health Ministry said the strikes killed six people, including four children, and wounded more than 40.

The ministry said 41 people, including two women of Russian nationality,  were also wounded.

People in Sanaa, Yemen, inspect the site of an airstrike by the Saudi-led coalition. (Hani Mohammed/Associated Press)

A Saudi-led coalition has been at war with the Houthis since 2015 and carries out near-daily airstrikes. The drone attacks on the pipeline marked one of the rebels’ deepest and most significant strikes inside Saudi territory since the conflict began.

The Saudi-led coalition acknowledged in a statement it had struck a number of Houthi targets on Thursday, including what it said were weapons depots and military sites.

Nuclear deal at core of dispute

At the root of the recent spike in Persian Gulf tensions appears to be U.S. President Donald Trump’s decision a year ago to pull the U.S. from Iran’s nuclear deal with world powers, embarking on a maximalist sanctions campaign against Tehran to cripple the country’s economy.

In response, Iran’s supreme leader issued a veiled threat Tuesday, saying it wouldn’t be difficult for the Islamic Republic to enrich uranium to weapons-grade levels. He also said that while his country would not negotiate with the United States, Iran is not seeking war.

Watch as Iran-U.S. tensions continue to heat up:

Tensions between Iran and the U.S. are rising amid attacks on U.S.-allied Saudi oil assets, as U.S. President Donald Trump makes thinly veiled statements about what might happen in the event of aggression against his country’s interests in the Persian Gulf. 2:05

On Wednesday, the U.S. State Department ordered all nonessential government staff to leave Iraq, and Germany and the Netherlands both suspended their military assistance programs in the country in the latest sign of tensions.

The movement of diplomatic personnel is often done in times of conflict, but what is driving the decisions from the White House remains unclear. Iraq is home to powerful pro-Iranian militias, while also hosting more than 5,000 American troops. The U.S. military’s Central Command said without elaborating that its troops were on high alert.

Last week, U.S. officials said they had detected signs of Iranian preparations for potential attacks on U.S. forces and interests in the Middle East, but Washington has not publicly provided any evidence to back up claims of an increased Iranian threat.

A senior British officer in the U.S.-backed coalition fighting ISIS appeared to push back against the U.S. claims, telling reporters earlier in the week that there had been no increased threat from Iranian-backed forces in Iraq and Syria. Maj.-Gen. Chris Ghika’s comments exposed international skepticism over the American military buildup.

Iran recently threatened it might resume higher enrichment by July 7, beyond the level permitted by the current deal between Tehran and world powers. The U.S. pulled out of the deal last year, reimposing sanctions that penalize countries and global companies that do business with Iran.

Though Iran maintains its nuclear program is for peaceful purposes, scientists say the time needed to reach the 90 per cent threshold for weapons-grade uranium is halved once uranium is enriched to around 20 per cent.