Oil prices climbed more ​than 4% to their highest in more than a month on Friday after the U.S. and ‌Iran stepped up attacks across the Gulf, with shipping threatened by a potential Red Sea closure on top of the restricted traffic through the Strait of Hormuz.

Brent crude futures settled $3.87, or 4.59%, higher to $88.10 a barrel, while U.S. West Texas Intermediate futures rose $3.54, or 4.48%, ​at $82.49. Both were at their highest since mid-June, Reuters reported.

For the week, both benchmarks gained about 16%, with Brent ​on track for a third consecutive weekly gain and WTI set for its second.

The two ⁠foes expanded fighting on Friday, with the U.S. striking bridges and an airport in Iran and Tehran hitting a power and ​desalination plant in Kuwait. Iran said it launched more strikes on U.S. facilities in the Middle East, including the first ​direct attack in Syria, after a sixth straight night of U.S. strikes on Iranian military facilities.

“The market is reacting to the increasing hostilities between Iran and the United States that have culminated this week with nightly attacks on Iranian infrastructure and retaliation by Iran on ​its neighbors’ infrastructure,” said Andrew Lipow, president of Lipow Oil Associates. “If more tankers come under fire and become damaged, ​we’re going to see oil prices continue to move up as shipowners simply refuse to enter the Persian Gulf.”

The collapsed truce between ‌the U.S. ⁠and Iran has resulted in a sharp decline in oil flows in the strait as Iran targets vessels transiting through it. Before the Iran war, about 20% of global oil supplies flowed through the waterway. Iran has pressed the Houthis to close the Red Sea route if the U.S. attacks Iran’s power infrastructure.

“Given that so much of Saudi Arabia’s exports have ​been redirected to the port ​of Yanbu via the East-West ⁠Pipeline to avoid Hormuz, any such development is a threat indeed,” Tamas Varga, analyst at PVM Oil Associates, wrote in a note.

Saudi Arabia has diverted more than 70% of ​its normal daily crude exports to the Red Sea port of Yanbu since the ​beginning of the ⁠war. Shipments from Yanbu averaged 4 million barrels per day in recent weeks, up from around 973,000 bpd in the same period last year.

Qatar’s defence ministry said its armed forces thwarted an Iranian missile attack early on Friday and the interior ministry said ⁠a ​child was wounded by shrapnel resulting from interception operations.

In a different conflict ​zone, Ukraine’s military said it struck a Russian oil refinery in the Yaroslavl region on Thursday.

US President Donald Trump has sent Congress formal notification that hostilities against Iran resumed on July 7, a letter his administration sees as opening a new 60-day window to use the military in the region without congressional approval, Reuters reported.

“I directed this military action consistent with my responsibility to protect Americans and United States’ national security and foreign policy interests,” Trump said in the letter, dated July 10, and seen by Reuters on Monday.

The letter outlines Trump’s actions including ordering a two-week ceasefire on April 7, which was extended, and his administration’s efforts to achieve a diplomatic solution to the conflict.

The United States began attacking Iran ⁠on February 28, alongside Israel.

Trump described the memorandum of understanding he signed with Iran on June 17, and said that Iran had violated it by attacking commercial vessels transiting the Strait of Hormuz, prompting him to order renewed strikes on the Islamic Republic.

As the conflict intensified, Trump said on Monday, the US was reinstating its blockade of Iranian shipping in the Gulf and would ensure the Strait of Hormuz stays open.

The US Constitution says that only Congress, not the president, has the power to declare war. However, US presidents have long claimed the right to order shorter military engagements without lawmakers’ approval to preserve US ⁠security, read the report.

The War Powers Act requires the president to inform Congress within 48 hours of initiating hostilities, and says military action begun without Congress’ approval must be terminated within 60 days.

With Iran, the first 60-day deadline was May 1, but the Republican president said it did not apply because he declared the hostilities had been terminated by ⁠the ceasefire, even as attacks continued and US forces blockaded Iranian ports.

Democrats and Republican opponents of the ongoing war said the administration was misinterpreting the law.
“The president can’t just wish away months of war he said would last ⁠only four to six weeks,” a senior House of Representatives Democratic aide said, commenting on condition of anonymity.

Additionally, the Senate and House both passed a resolution last month directing Trump to withdraw US forces ⁠from hostilities with Iran, despite his fellow Republicans’ slim majorities in both chambers, Reuters reported.

The votes reflected growing concern about the months-long conflict.

Trump lashed out after the vote, accusing those who voted in favor of providing “comfort” to Iran and making his job “more difficult.”

Yemen’s defense ministry says that its armed forces targeted the runway at Sanaa International Airport to prevent an Iranian plane from landing.

Yemen’s capital Sanaa is under the control of the Iran-aligned Houthi group, while the internationally recognized government, which has the backing of Saudi Arabia and other Gulf states, operates out of Aden in southern Yemen.

Houthi movement accused Saudi ​Arabia of launching air strikes against the international ‌airport in Sanaa, and vowed to retaliate, Reuters reported.

Houthi military spokesperson Yahya Saree called the attacks “blatant aggression” and said it had ended a period of de-escalation in ​the long-running conflict. He said Saudi Arabia would bear the ​consequences and that the attack would not go unanswered.