Veteran diplomat Alina Romanowski was sworn in as the US ambassador to Iraq, amid mounting internal and external security threats faced by the Arab nation.
US Vice President Kamala Harris swore in Ms Romanowski in a ceremony on Tuesday.
Ms Romanowski, who was confirmed by the US Senate in March, has more than four decades of experience across various US government agencies.
She most recently served as US ambassador to Kuwait, after holding positions in the State and Defence departments, as well as working in intelligence.
Ms Romanowski succeeds departing ambassador Matthew Tueller.
During her confirmation hearings, Ms Romanowski said Iraq "remains a foreign policy priority for the United States and is a cornerstone of regional stability".
The diplomat told a Senate committee in March that she would continue to find long-lasting solutions to the most vulnerable populations in Iraq.
"The United States supports a stable, prosperous and democratic Iraq that serves all its citizens, including its most vulnerable and marginalised communities," she told the Senate foreign relations committee.
Ms Romanowski said strengthening political, economic and civil society groups would be one of her leading priorities as ambassador.
"If confirmed, bolstering Iraq’s independence and advancing citizen rights will be a top priority in my engagements with Iraq’s new government," she said.
Ms Romanowski said she would urge Iraq to diversify its economy and work to strengthen the country's security institutions.
Iraq's security challenge could be a pressing matter early in Ms Romanowski's tenure as ambassador.
Pro-Iranian forces last year launched missile strikes at Baghdad's Green Zone, where the US embassy is situated. Iraqi security forces said at the time they had prevented an attempt to attack a convoy at a military base where US-led international coalition troops were stationed.