The United States is deploying about 9,000 additional troops to the Middle East, the largest build-up of American forces in the region in years, as tensions with Iran continue to rise.

The deployment includes roughly 7,000 sailors and 2,000 Marines, according to reports. The USS Theodore Roosevelt carrier strike group and the USS Makin Island amphibious ready group are heading to the region.

Officials have also signalled that a third aircraft carrier could arrive by the end of October, which would give the US an unprecedented naval presence near Iran.

In total, more than 20,000 American personnel are expected to be stationed across the region once the deployment is complete.

The build-up follows weeks of escalating rhetoric between Washington and Tehran. US officials say the deployment is defensive and aimed at deterring attacks on American forces and allies.

Iranian leaders have responded with warnings of their own. An Iranian lawmaker said this week that any US attack would open "new fronts" and trigger a missile response.

The deployment comes as oil markets react nervously, with Brent crude climbing above $102 a barrel on fears of supply disruptions in the Gulf.