Gilday, the Joint Staff director, says the latest decision to send 1,500 additional troops to the Middle East will boost surveillance of Iranian forces and their proxies.
Washington continues to amass forces in the Middle East as the Pentagon accuses Iran of an "ongoing threat" to USA allies and interests.
The forces would help strengthen US defenses in the region, two sources told Reuters earlier on condition of anonymity.
Vice Admiral Michael Gilday says the US has a high degree of confidence that Iran's Revolutionary Guard was responsible for the explosions on four tankers, and that Iranian proxies in Iraq fired rockets into Baghdad.
Tensions in the Middle East have escalated quickly over the last several weeks after attacks were made on Israel earlier this month, which former Israeli national security adviser Yaakov Amidror said Iran was behind.
This is a developing story.
"This is a prudent response to credible threats from Iran", said Acting Defence Secretary Patrick Shanahan.
The administration had notified Congress earlier in the day about the troop plans.
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"We want to have protection in the Middle East".
"The additional deployment to the U.S. Central Command area of responsibility is a prudent defensive measure and meant to reduce the possibility of future hostilities", Shanahan added.
Mr Shanahan said he had "approved a request from the combatant commander for additional resources" in the region. "Eager to avoid escalation with Iran amid already heightened tensions, Pentagon officials stressed the defensive nature of the deployment in a news briefing and noted that none of the troops would be heading to hot spots like Iraq or Syria".
"We think that through a combination of a very measured deployment of assets as well as public messaging, we are again trying to underscore that we are not seeking hostilities with Iran".
Yemen, there are Houthi rebels who are fighting Saudi Arabia and backed by Iran, but there are also tens of thousands of civilians who have been caught up in that war and who have been casualties in that war, mostly because of these bombs dropped by the Saudi-led coalition.
The president has argued that the nuclear deal failed to sufficiently curb Iran's ability to develop nuclear weapons or halt its support for militias throughout the Middle East that the USA argues destabilize the region. "And I certainly don't think they want to fight with us", Trump said.
It's possible that in the future additional U.S. Navy ships could be sent to the region beyond the USS Abraham Lincoln Strike Group and the USS Kearsarge Amphibious Group that are now in the North Arabian Sea.
The president has argued that the nuclear deal failed to sufficiently curb Iran's ability to develop nuclear weapons or halt its support for militias throughout the Middle East that the US argues destabilize the region.