US lawmakers said a State Department inspector-general - unexpectedly dismissed by President Donald Trump last month - confirmed on Wednesday that he was investigating a "national emergency" to justify arms sales to Saudi Arabia when he was sacked.

Inspector General Steve Linnick was sacked on May 15, becoming the fourth government watchdog to be dismissed by the Republican president in the past few months.

In a statement, House Speaker Elliott Engel and other Democratic members of the House said in a statement that Lenik had also confirmed in an interview with members of Congress that he was investigating allegations that Secretary of State Mike Pompeo and his wife had misused the ministry's resources.

The inspector general is tasked with preventing fraud and misusing public money.

The Democrats opened an investigation, including Wednesday's meeting of the House of Representatives Foreign Affairs Committee and the Senate Foreign Relations Committee with Linnik. The interview was conducted remotely and lasted for about seven hours.

Pompeo had said he had asked Trump to fire Linnick, but he had not given a reason for the request.

On their part, members of Congress said Linnick was investigating Trump's decision to declare a national emergency last year to sell weapons to Saudi Arabia despite congressional objections, as well as allegations that Pompeo and his wife used an employee who gets paid from taxpayer money for personal tasks.

Pompeo Trump recommended sacking Steve Link (Reuters)

Arguments and justification

About two weeks ago, the American CNN network said it had learned from its sources that Pompeo had asked his ministry officials to search for arguments to justify the emergency decision he issued last year to expedite a huge arms deal for Saudi Arabia.

A US State Department official said they disclosed Pompeo's behavior to the department's inspector general’s office late last year, as part of an investigation the office opened on that emergency decision that expedited the $ 8 billion arms deal to Saudi Arabia, and avoided it going through Congressional reviews.

The CNN report came in light of suspicions hovering over Pompeo, after US President Donald Trump issued a decision to dismiss the State Department's inspector-general, Steve Link, on the recommendation of Pompeo.

However, the minister denied in press statements that his recommendation came in retaliation against Linnik, and he said he was not aware of the investigations carried out by the ministry's inspector general's office, but at the same time he did not reveal the reason for his recommendation to remove this inspector.