Washington: Ashton Carter was sworn in Tuesday as the 25th US defense secretary -the fourth in US President Barack Obama`s six years in office.
After taking the helm, he will have to tackle mounting issues, such as the fight against the extremist group Islamic State (IS) and a decision on whether to arm the Ukrainian forces with lethal weapons.
Carter`s inauguration also came at a time when the Yemeni government, a key US Middle East partner in fighting Al Qaeda, was on the verge of collapse, threatening US counter-terrorism strategy across the region, according to Xinhua.
At his Feb 4 Senate Armed Service Committee hearing, Carter, a former deputy defense secretary described the work that lies ahead for him and Pentagon as unprecedented.
"I think we are in a time where the number and severity of risks is something I`ve not seen before in my life," he said.
Another challenge for Carter will come from the US Congress on the 2016 Pentagon budget. The Obama administration recently sought a base defence budget of $534 billion when it sent its 2016 spending request to Congress, $35 billion more than a federal budget cap imposed in 2011.