The Senate vote on confirmation of Mike Pompeo as Secretary of State is projected on the live congressional feed by the C-Span network.
His predecessor, Rex Tillerson, was sacked last month by the president via Twitter amid a personality clash.
"From North Korea's nuclear threats to Iran's aggression, Mike's confirmation as Secretary of State comes at a critical time for USA foreign policy", said Ed Royce (R-CA), the chairman of the House Foreign Affairs Committee. Trump sent Pompeo to North Korea three weeks ago to meet with the country's leader, Kim Jong Un, ahead of a summit with the U.S. president to address Pyongyang's nuclear program.
Pompeo overcame stiff opposition in the Senate from Democrats who warned he would add fuel to Trump's aggressive foreign policy.
"Whether it's his support for interrogation techniques that amount to torture, his preference for war over diplomatic solutions or his hateful, blatantly discriminatory views about Muslim and LGBTQ Americans, Mike Pompeo's confirmation would. erode our moral standing on the world stage", she said in a floor speech.
The deadline for Trump to renew the Iran deal is approaching and the president is expected to meet with Kim in May or June.
The president - a property magnate and reality television star with no background in foreign policy - has chafed against many of his national security advisors.More news: US EPA chief Pruitt tells lawmakers ethics charges are distractions, lies
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Pompeo served in the military for five years - although never saw combat - and then left to attend Harvard Law School.
While heading the CIA, Pompeo was said to have utilised a "gloves off" approach in engaging the Taliban in Afghanistan.
"Hard to believe Obstructionists May vote against Mike Pompeo for Secretary of State".
The vote on Pompeo's nomination comes as the United States faces multiple crises around the world coming to a head next month.
Within hours of his landing in Europe, he will preside over a breakfast meeting at North Atlantic Treaty Organisation headquarters to discuss new measures to counter an increasingly aggressive Russian president, Vladimir V. Putin, who USA intelligence officials say has ordered the annexation of Crimea, intervention in Ukraine, the hacking of the American election in 2016 and murders or attempted murders of countless rivals, including a former Russian spy living in Britain. But in his confirmation hearing, Mr. Pompeo promised to try to preserve the accord, one of several pledges he made that were at odds with his record as a four-term Tea Party congressman from Kansas.
"He obviously has the president's support".
Just after Pompeo's vote, the Senate is expected to vote on Richard Grenell to be the next Ambassador to Germany.
"He is strongly pro-life and committed to upholding the dignity of every human being as America's top diplomat".