The US Defense Department will be upgrading and expanding military facilities in Guam and Australia, underscoring its focus on China as the country's leading defense rival, an official said.

The details of the "global posture review," commissioned by President Joe Biden's administration early this year, would remain classified, the official added, so as not to disclose plans to rivals.

The review confirmed the priority region for the US military was the Indo-Pacific, said Mara Karlin, a top Pentagon policy official.

The review "directs additional cooperation with allies and partners across the region to advance initiatives that contribute to regional stability and deter potential military aggression from China and threats from North Korea," she told reporters.

In addition, it "strengthens the combat-credible deterrent against Russian aggression in Europe and enables NATO forces to operate more effectively."

As for the Middle East, Karlin pointed out that global responsibilities "require us to make continuous changes to our Middle East posture, but we always have the capability to rapidly deploy forces to the region based on the threat environment."

However, "in Australia, you'll see new rotational fighter and bomber aircraft deployments, you'll see ground forces training and increased logistics cooperation," confirmed Karlin.

Asked if the review foresaw more increases in the US presence in the Pacific region, Karlin said, "We're moving the needle a bit."  

"And what I'd like to think is, over the coming years, you will see that needle move more," she said.

In Europe, Biden reversed a decision to reduce the number of US military personnel deployed in Germany to 2,500, and reiterated the US commitment to NATO, after it was questioned by his predecessor, Donald Trump.

In Iraq, Washington concluded an agreement with the Iraqi government that stipulates the departure of all forces by the end of the year, but about 2,500 US military personnel remain present on Iraqi soil.

"DOD posture will continue to support the defeated Islamic State campaign and build the capacity of partner forces," the official confirmed.