The State Department watchdog abruptly fired by President Donald Trump was also probing his controversial bypassing of Congress to sell weapons to Saudi Arabia, a Democratic lawmaker said Monday.

Representative Eliot Engel, who leads the House Foreign Affairs Committee, earlier said that Inspector General Steve Linick was sacked late Friday after he opened an investigation into Secretary of State Mike Pompeo.

"I've learned there may be another reason for IG Linick's firing. His office was investigating -- at my request -- Trump's phony emergency declaration so he could send Saudi Arabia weapons," Engel wrote on Twitter.

"We don't have the full picture yet, but it's troubling that Sec Pompeo wanted Linick pushed out," he wrote.

Pompeo in May 2019 said there was a state of emergency with Iran, allowing the Trump administration to bypass Congress and sell $8.1 billion in arms to Saudi Arabia and other Arab allies.

US Secretary of State Mike Pompeo, meeting with Saudi Arabia's Crown Prince Mohammed bin Salman at Irqah Palace in the capital Riyadh in February 2020
US Secretary of State Mike Pompeo, meeting with Saudi Arabia's Crown Prince Mohammed bin Salman at Irqah Palace in the capital Riyadh in February 2020 POOL / ANDREW CABALLERO-REYNOLDS

The move infuriated lawmakers, who had tried to block the sale on the grounds that the weapons were killing civilians in Yemen, which Saudi Arabia has widely bombed as it fights Huthi rebels linked to Iran.

Engel and Robert Menendez, the top Democrat on the Senate Foreign Relations Committee, earlier said that the firing of Linick "may be an illegal act of retaliation" and vowed to investigate.

A Democratic congressional aide, speaking on condition of anonymity, said the inspector general was looking into complaints about how Pompeo and his wife, Susan Pompeo, used a State Department employee.

Linick had heard a complaint that the Pompeos made the staffer walk the family dog, pick up their dry-cleaning and make dinner reservations for them, the congressional aide said.