The increase in Washington's military presence in the Middle East comes as the growing Israel-Hezbollah conflict -- which saw Israel kill the Lebanese militant group's leader Hassan Nasrallah last week -- raises fears of a wider regional war.

"A certain number of units already deployed to the Middle East region... will be extended, and the forces due to rotate into theater to replace them will now instead augment" those that are already there, Deputy Pentagon Press Secretary Sabrina Singh told journalists on Monday.

"These augmented forces include F-16, F-15E, A-10, F-22 fighter aircraft and associated personnel," Singh said, later adding that there will be "an additional few thousand" personnel in the region as a result.

The US Central Command announced Tuesday that three additional squadrons of warplanes were arriving in the region, while one was already present.

Israel announced Tuesday that Defense Minister Yoav Gallant had briefed US Defense Secretary Lloyd Austin on "localized and targeted" ground operations targeting Hezbollah positions in South Lebanon -- a further escalation of the conflict after a week of intense air strikes that killed hundreds.

Austin said the previous evening that he had offered support to Gallant for "dismantling attack infrastructure" belonging to Hezbollah along the border with Lebanon.

He also warned Iran of "serious consequences" should it directly strike Israel in response to its attacks on the Tehran-backed militant group.