The Pentagon is sending an additional aircraft carrier and 10,000 sailors and Marines to the Persian Gulf, giving American commanders more options if President Trump chooses to escalate attacks on Iran, a U.S. official told Bloomberg on Friday.

The official said the USS Theodore Roosevelt left its home port in San Diego on Sunday, bound for the Middle East. On Monday, the USS Makin Island amphibious readiness group, carrying an assault ship, aircraft and 2,200 Marines, also sailed for the region, while the USS Boxer amphibious readiness group is operating near the Strait of Hormuz.

Once the Roosevelt arrives, the United States could again have three carrier strike groups in the area, the same number as in late April, though no decision has been made to maintain that level, the official said. The USS George Washington remains in the region and the USS George H.W. Bush has temporarily departed. Before this year’s operations against Iran, the last time the Navy kept three carriers in the Middle East was 2003, supporting the opening phase of the Iraq invasion.

U.S. Central Command, which oversees operations in the region, declined to confirm the movements. “We don’t discuss unit schedules for operational security reasons,” it said in a statement.

The deployments follow Mr. Trump’s remark that increased military strikes on Iran were “possible” after the November midterm elections. Separately, the United States has sent two additional missile batteries in recent weeks to protect oil and gas facilities in Qatar and Saudi Arabia, Axios reported, citing two American officials and one regional source. That move was meant to reassure security partners that Washington would protect key energy installations if new attacks are ordered, Axios said.

Keeping three carriers in the region would compound the Navy’s readiness problems, said Ronald O’Rourke, a longtime analyst of naval forces who recently retired from the Congressional Research Service. The strain is already visible: the USS Abraham Lincoln arrived in Thailand last month after a nine-month deployment, and the USS Gerald Ford, sent to the Middle East after supporting operations against Venezuela, spent 11 months at sea. “Maintaining even a two-carrier presence in that area over an extended period of time would be a strain for the carrier force,” Mr. O’Rourke said. “Maintaining a three-carrier presence in that area for an extended period would be a significantly greater strain.”

Investors reacted to the prospect of a new flare-up by weighing the inflation risk of higher oil prices against signs the Federal Reserve may take a more measured approach to further tightening. Brent crude rose 0.4 percent to $102.74 a barrel, after gaining 4 percent on Thursday.

Major U.S. and Iranian strikes have paused while both sides try to revive diplomacy, but talks to end the war, now in its eighth month, remain deadlocked over issues including Tehran’s control of the Strait of Hormuz. Mr. Trump was reported to have rejected an Iranian offer to reopen the strait within seven days if Washington lifted its blockade, and Iran’s foreign minister, Abbas Araghchi, has suggested in recent private talks that Tehran would restore nuclear inspectors’ access to bombed facilities in exchange for sanctions relief.