Trump blames Iran for tanker attacks, calls for talks

President Donald Trump has blamed Iran for attacks on oil tankers near the strategic Strait of Hormuz, but he also held out hope that implicit US threats to use force will yield talks with the Islamic Republic as the Pentagon considers beefing up defences in the Persian Gulf area.

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 on 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!"

Trump last year withdrew the United States from an international agreement to limit Iran's nuclear program that was signed in 2015 under his predecessor, President Barack Obama.

He has since then re-instated economic sanctions aimed at compelling the Iranians to return to the negotiating table.

Just last month the US ended waivers that allowed some countries to continue buying Iranian oil, a move that is starving Iran of oil income and that coincided with what US officials called a surge in intelligence pointing to Iranian preparations for attacks against US forces and interests in the Gulf region.

In response to those intelligence warnings, the US on May 5 announced it was accelerating the deployment of the USS Abraham Lincoln aircraft carrier battle group to the Gulf region.

It also sent four nuclear-capable B-52 bombers to Qatar and has beefed up its defences in the region by deploying more Patriot air defence systems.

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.

At the Pentagon, acting Defense Secretary Patrick Shanahan said Iran is not just a US problem. He said the US goal is to "build international consensus to this international problem," and to ensure that US military commanders in the region get the resources and support they need.

In remarks to reporters later, Shanahan noted the commercial and strategic importance of the Strait of Hormuz, through which passes about 20 per cent of the world's oil.

"So, we obviously need to make contingency plans should the situation deteriorate," he said.

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 the 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.

Rep. Elissa Slotkin, D-Mich., said that providing naval escorts through the Strait of Hormuz is an option, but, "I don't think it's a sustainable option because of the amount of traffic."

She said tanker warfare in the Persian Gulf has historically been a problem, and she wouldn't be opposed to the U.S. having a more visible presence in the region.

Slotkin, a former senior policy adviser at the Pentagon, said she is concerned that the Trump administration does not have a clear strategy on Iran. She said it's difficult to deter Iran without provoking additional violence, adding, "I don't believe this administration is capable of walking such a deft, fine line."

In ticking off a list of Iranian acts of "unprovoked aggression," including Thursday's oil tanker attacks, Secretary of State Mike Pompeo added a surprise accusation.