Washington, DC - US Secretary of State Mike Pompeo was grilled on Friday by Democrats on a House panel over the United States killing of top Iranian commander Qassem Soleimani and the US response to the coronavirus.

Appearing before the House Foreign Affairs Committee for two hours, Pompeo defended President Donald Trump's decision to order the assassination of Soleimani, claiming Americans in the Middle East are safer now because Iran has been deterred from aggression.

"We made clear that we are willing and able to impose costs on our adversaries if they threaten or attack us," Pompeo told the committee in the long-awaited hearing that also included a number of questions on the coronavirus.

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The Trump administration has offered shifting explanations for the air attack that killed Soleimani and several others at the airport in Baghdad, Iraq.

Initially, the president and his advisers said they had information that Soleimani was planning an "imminent attack".

Later, in a legally mandated report to Congress, the Trump administration abandoned that claim and argued prior attacks planned by Soleimani against US forces, coupled with rising provocations from Iranian-backed armed groups in Iraq justified the strike.

"One hundred percent in a very short timeframe, he was in the region actively plotting to kill Americans," said Pompeo, who appealed to the fractious committee on Friday for support for Trump's policy towards Iran.

Two Democratic members of the House of Representatives Abigail Spanberger and Joaquin Castro said the intelligence information provided by the administration to Congress behind closed doors in the days after the strike did not show an imminent threat.

"I have seen that classified information and after reviewing it, I don't think that you are telling us the truth," Castro told Pompeo pointedly.

Women hold pictures of Iranian Major-General Qassem Soleimani, head of the elite Quds Force, who was killed in an air strike at Baghdad airport, during a funeral procession and burial at his hometown in Kerman, Iran [File: Mehdi Bolourian/Fars News Agency/WANA/Reuters]

Spanberger, a former intelligence agency officer, said: "Your own report directly contradicts what you and the president told the American people over and over.

"With conflicting information, it is hard for the American people to know what to believe," she said.

Pompeo dismissed the accusations and argued Soleimani's role as head of Iran's Quds Force tied him to the deaths and injuries of as many as 600 US troops during the Iraq war.

"We conducted this attack fully inside our constitutional and statutory authority and the action the president took was fully lawful," Pompeo said.

"We had communicated clearly that the loss of American lives would incur real consequences," he added.

Trump has pursued a "maximum pressure" campaign against Iran designed to confront Iranian influence in the region and weaken its economy through sanctions after unilaterally pulled the US out of the Iran nuclear deal in May 2018.

Coronavirus fears

Pompeo was also peppered with questions from Democrats about the rising fears in the US of the coronavirus outbreak. The first case of local infection of an American who had not travelled to or been in contact with someone that had travelled to China, where the virus originated, was identified in California on Wednesday.

Trump has come under pressure by Democrats to take greater action against the virus. Earlier this week, Trump attempted to quell fears and appointed Mike Pence to oversee the federal government's effort to contain the virus - a move Democrats criticised, citing the vice president's lack of expertise on public health issues.

"Arrogance. Arrogance," said Representative David Trone, a Democrat. "The administration's track record of mishandling crises doesn't inspire confidence."

Democratic Representative Ted Deutch also criticised the administration, saying that Trump's "pattern of misinformation undermines our entire system".

COVID-19, the formal name for the illness caused by a new coronavirus, emerged in the Chinese city of Wuhan in December. More than 83,000 cases have been confirmed worldwide and more than 2,800 people have died as a result of the virus, the majority of whom were in China. No deaths linked to the virus have been reported in the US.

US President Donald Trump holds a document about the coronavirus as he gives a news conference at the White House [Carlos Barria/Reuters]

Health officials in California, which has a population of 40 million, are monitoring 8,400 people for potential infection, the state's governor said on Thursday. Testing has been limited because test kits initially provided to the state by the US Centers for Disease Control (CDC) were faulty.

Pompeo defended the Trump administration's response to the virus, saying the US has made offers to help Iran, which has been hit hard by the outbreak.

"We have made offers to the Islamic Republic of Iran to help, and we've made clear to others around the world and the region that assistance, humanitarian assistance to push back against the coronavirus in Iran is something the United States of America fully supports. We will continue to support. That's true for every nation," Pompeo said.

Later on Friday, Iran's foreign ministry spokesman reportedly said that any US offer to help Iran in its fight against the coronavirus was "ridiculous".

"The claim to help Iran in dealing with corona from a country who with their economic terrorism has created widespread pressure for the people of Iran and even closed the paths for buying medicine and medical equipment is a ridiculous claim and political-psychological game," Abbas Mousavi was quoted by Iran's semiofficial Mehr news agency as saying.