US Defense Secretary Lloyd Austin arrived in Iraq on Tuesday for an unannounced visit, just two weeks before the 20th anniversary of the US-led invasion that toppled Saddam Hussein.

 "I am here to reaffirm the US-Iraqi strategic partnership as we move toward a safer, more stable and more sovereign Iraq," Austin tweeted as he landed in Baghdad.

 Austin's visit comes after he held talks in neighboring Jordan with King Abdullah II, a staunch US ally in the region.

 "Secretary Austin shared his concerns on a number of shared issues, including ... a focus on security and stability in Iraq and countering other destabilizing actions in the region," the Pentagon said in a statement.

 His visit comes on the 20th anniversary of the ground invasion that started two decades of bloodshed that Iraq is only now beginning to shake off.