A day after explosions blew holes in two oil tankers just outside Iran's territorial waters, rattling international oil markets, the administration seemed caught between pressure to punish Iran and reassure Washington's Gulf Arab allies without drawing the US closer to war.

"Iran did it," Trump said Friday on Fox News Channel's "Fox & Friends." He didn't offer evidence, but the US military released video it said showed Iran's Revolutionary Guard removing an unexploded mine from one of the oil tankers targeted near the Strait of Hormuz, suggesting Tehran wanted to cover its tracks.

By pointing the finger at Iran, Trump was keeping a public spotlight on an adversary he accuses of terrorism but also has invited to negotiate. The approach is similar to his diplomacy with North Korea, which has quieted talk of war but not yet achieved his goal of nuclear disarmament. Iran has shown little sign of backing down, creating uncertainty about how far the Trump administration can go with its campaign of increasing pressure through sanctions.

Iran denied any involvement in the attacks and accused Washington of waging an "Iranophobic campaign" of economic warfare.

A US Navy team on Friday was aboard one of the tankers, the Japanese-owned Kokuka Courageous, collecting forensic evidence, according to a US official who spoke on condition of anonymity to discuss a sensitive operation.

Apparently alluding to the US video, Trump said Iran's culpability had been "exposed." He did not say what he intended to do about it but suggested "very tough" US sanctions, including efforts to strangle Iranian oil revenues, would have the desired effect.

"They've been told in very strong terms we want to get them back to the table," Trump said. Just a day earlier, the president took the opposite view, tweeting that it was "too soon to even think about making a deal" with Iran's leaders. "They are not ready, and neither are we!"

Officials said that Pentagon deliberations about possibly sending more military resources to the region, including more Patriot missile batteries, could be accelerated by Thursday's dramatic attack on the oil tankers.

Other administration officials said the US is re-evaluating its presence in the region and will discuss the matter with allies before making decisions. The officials, who briefed reporters on condition of anonymity, said Thursday the US is looking at all options to ensure that maritime traffic in the region is safe and that international commerce, particularly through the Strait of Hormuz, is not disrupted. One option, they said, is for US and allied ships to accompany vessels through the strait, noting that this tactic has been used in the past. They said there is no timeline for any decisions.

Australian Associated Press