The United States will send about 1,000 additional troops to the Middle East in response to heightened tensions with Iran over last week's attacks on two oil tankers near the Strait of Hormuz, acting Defense Secretary Patrick Shanahan said Monday.

The move is intended to "address air, naval and ground-based threats in the Middle East," and "ensure the safety and welfare of our military personnel working throughout the region," Shanahan said in a statement.

Referring to Thursday's attacks, he said, "The recent Iranian attacks validate the reliable, credible intelligence we have received on hostile behavior by Iranian forces and their proxy groups that threaten United States personnel and interests across the region."

President Donald Trump has blamed Iran for the attacks, one of which involved a Japanese-operated tanker. Tehran has denied involvement.

Despite the planned dispatch of additional troops, Shanahan said, the United States does not seek conflict with Iran.

In a related move, the Pentagon released new images it said showed Iran's Islamic Revolutionary Guard Corps removing an unexploded mine from the side of the attacked Japanese tanker Kokuka Courageous.

Other photos showed a large hole on the side of the vessel, above the water line, that officials said appears to have been caused by another mine.

The Pentagon released the photos to bolster its claim that Iran was responsible for the attacks on the Kokuka Courageous and another oil tanker.

Earlier Monday, the White House denounced Iran's announcement that it will soon exceed limits on the amount of low-enriched uranium it can possess under a 2015 nuclear deal, calling it "nuclear blackmail."

"The regime's nuclear blackmail must be met with increased international pressure," National Security Council spokesman Garrett Marquis said.

In a brief tweet, Trump warned, "Iran to defy Uranium Stockpile Limits."

The nuclear deal, which Iran and other signatories have observed even after the U.S. withdrawal in May 2018, caps Tehran's stock of low-enriched uranium at 300 kilograms enriched to up to 3.67 percent.

But Iran Atomic Energy Organization spokesman Behrouz Kamalvandi said Monday, "Countdown to surpass the 300-kilogram limit for enriched uranium stockpile begins today and we will surpass the limit in 10 days on June 27."

Marquis said Iran's enrichment plans "are only possible because the horrible nuclear deal left their capabilities intact."

"President Trump has made it clear that he will never allow Iran to develop nuclear weapons," he said.

Under the deal involving Iran and six powers -- Britain, China, France, Germany, Russia and the United States -- Iran agreed to curb its nuclear activities in exchange for the lifting of economic sanctions.