The Pentagon will re-evaluate a plan to grow the US fleet to 355 ships, a move that experts worry could diminish the service’s presence as Iran poses a renewed challenge to Middle East waterways through proxy groups.

Speaking at the Pentagon earlier this month, the Navy’s top officer said that the decision, which will be paired with the US administration’s new budget, was made to align the maritime service’s mission with the Defense Department’s new strategy that focuses on China and Russia.

“In light of the new National Defense Strategy and changes in the security environment since that was put out, we’re doing a new force structure assessment,” Chief of Naval Operations Adm. John Richardson told reporters. “We’ll see where that goes.”

The Navy currently has 288 deployable ships, about a third of which are currently deployed overseas, and has typically kept two of its three forward-deployed aircraft carriers in the Persian Gulf, according to a recent study by Chatham House. The US Fifth Fleet, based in Manama, Bahrain, houses about 7,000 American troops.