The leader of an Iran-backed Iraqi militia has vowed to retaliate against America for the deaths of four of his men in an airstrike along the Iraq-Syria border last month, calling it a military operation that everyone will remember.

In an interview in Baghdad, Abu Alaa al-Walae, commander of Kataib Sayyid al-Shuhada, said that the election of Iran’s hardline judiciary chief Ebrahim Raisi as president will strengthen Iran-backed militant groups across the Middle East for the next four years.

Al-Walae spoke to foreign media on Monday in an office in a Baghdad neighborhood along the Tigris River. On June 27, US Air Force planes carried out airstrikes near the Iraq-Syria border against facilities used by Iran-backed militia groups to support drone strikes inside Iraq, according to the Pentagon. Four members of the militia were killed.

The Popular Mobilization Forces, an Iraqi state-sanctioned umbrella of mostly Shiite militias, including those targeted by US strikes, said their men were on missions to prevent Islamic State infiltration and denied the presence of weapons warehouses.

The day after the airstrikes, US troops in eastern Syria were targeted by rocket fire, but no casualties were reported. The United States has blamed Iran-backed militia groups for attacks, most of which were rocket strikes, on the American presence in Baghdad and military bases throughout Iraq. Attacks have recently become more sophisticated, with militants employing drones.

US military officials have grown increasingly concerned about drone attacks on US military bases in Iraq, which have become more common since a US-directed drone killed Iranian Gen. Qassem Soleimani near Baghdad airport last year. The attack also killed Iraqi militia leader Abu Mahdi al-Muhandis. The strike infuriated mostly Shiite Iraqi lawmakers, prompting parliament to pass a nonbinding resolution urging the Iraqi government to withdraw foreign troops from the country.

An explosives-laden drone struck the military section of the international airport in Irbil, Iraq’s northern Kurdish-run region, in mid-April, causing no casualties or damage. American troops are also stationed at the base.

According to US officials, Iran-backed militias have carried out at least five drone attacks since April.

The bearded al-Walae, dressed in black slacks and an olive-green baseball cap, hinted that his militia might use drones in future attacks but did not elaborate. When asked if they had previously used drones against American troops in Iraq, he gave no direct answer and moved on to other topics.

Al-Walae spoke in an office with a poster of Soleimani on the wall. Al-Walae had a framed photo of himself standing next to Sayyed Hassan Nasrallah, the leader of Lebanon’s Hezbollah group, on a table next to him.

He praised Iran’s new president, Hassan Rouhani, who is set to take office next month, and predicted that Iran-backed militant groups would “have their best times.” Raisi stated in his first remarks following his election last month that he rejects the possibility of meeting with President Joe Biden or negotiating Tehran’s ballistic missile program and support for regional militias.

Al-Walae, who was once imprisoned by US troops in Iraq, boasted that his men were among the first to travel to neighboring Syria to fight alongside President Bashar Assad’s forces in 2012, a year after the country’s civil war began. He stated that their first mission was to protect a Shiite holy shrine south of Damascus. Later, they fought in various parts of Syria. Iran-backed fighters from across the region have joined the Syrian conflict, tipping the scales in Assad’s favor. Thousands of Iran-backed fighters remain in Syria, with many stationed near the Iraqi border in the towns of Boukamal and Mayadeen.

Al-Walae also stated that he does not expect Iraq’s parliamentary elections to be held on time in October, and that they may be postponed until April of next year. He blamed the delay on the country’s deep crisis, which included severe power outages during the scorching summer.