Barbara Leaf, the new head of the US State Department’s Middle East bureau, said she was "deeply optimistic" about opportunities for partnerships between the US and the region, but warned of challenges such as tackling Iran's "destabilising activities".
Ms Leaf, who served as the US ambassador to the UAE from December 2014 to March 2018, was confirmed by the US Senate last month.
"I've spent much of my career working in this vital region building partnerships between the US and our friends, and I'm humbled and honoured to lead the talented team in Washington that is focused on the same," she said in a video posted on Twitter on Tuesday.
"We're deeply optimistic about the opportunities that lay ahead of us ... (but) at the same time, I'm clear-eyed about the challenges that await me, such as finding ways to address Iran's destabilising activities, and working with our partners to end conflicts in Yemen, Syria and Libya."
Ms Leaf said sustainable security was key and noted that the US commitment to the region was "firm".
"I'm proud that our diplomatic tools will lead that commitment," she said.
"We're embracing innovation, partnerships in the region, a dialogue about human rights, and we're advancing real and sustainable prosperity."
Ms Leaf has also served as the deputy assistant secretary of state for the Arabian Peninsula, deputy assistant secretary of state for Iraq, and the State Department’s first director of the Office of Iranian Affairs.
A career diplomat, she served throughout the region in the past 25 years.
She held posts in Tunis, Basra, Kuwait City, Cairo and Jerusalem, and speaks Arabic, French, Italian and Serbo-Croatian, the State Department said.
