Washington (CNN) The US will send 1,000 additional US forces and more military resources to the Middle East amid tensions with Iran , the Pentagon announced Monday.

"In response to a request from the US Central Command for additional forces, and with the advice of the Chairman of the Joint Chiefs of Staff and in consultation with the White House, I have authorized approximately 1,000 additional troops for defensive purposes to address air, naval, and ground-based threats in the Middle East," acting Defense Secretary Patrick Shanahan said in a statement.

"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," Shanahan said, adding that the "United States does not seek conflict with Iran."

Shortly before the announcement the Pentagon released a detailed set of photos that it said showed Iranian boats removing a mine from one of two tankers attacked in the Gulf of Oman on June 13. The US attributes the attack to Iran. Tehran has vigorously denied the charge.

"The action today is being taken to ensure the safety and welfare of our military personnel working throughout the region and to protect our national interests," Shanahan said. "We will continue to monitor the situation diligently and make adjustments to force levels as necessary given intelligence reporting and credible threats."

One US official says the deployment will include intelligence, surveillance and reconnaissance aircraft and missile defense for force protection.

News of the additional troop deployment comes as the State Department announced Monday that Secretary of State Mike Pompeo will travel Tuesday to the command center that oversees Middle East military operations.

A day earlier, Pompeo said the Trump administration is still mulling military action against Iran.

The State Department announced Pompeo's trip to US Central Command in Florida after a senior Iranian official told CNN that the US and Iran are headed toward "a confrontation which is very serious for everybody in the region." Separately, Iran announced Monday that it will break uranium stockpile limits set by the international nuclear pact the Trump administration pulled the US out of in May 2018.

House Speaker Nancy Pelosi acknowledged the tensions with Iran in a statement late Monday but urged the administration to brief Congress on the "deeply concerning decision."

"Americans must have no illusions about the Iranian regime, and must remain committed to holding Iran accountable for its dangerous activities in the region. But we must be strong, smart and strategic -- not reckless and rash -- in how to proceed," the California Democrat's statement said.

"The Congress must be immediately briefed on the administration's decisions and plans. This deeply concerning decision may escalate the situation with Iran and risk serious miscalculations on either side. Diplomacy is needed to defuse tensions, therefore America must continue to consult with our allies so that we do not make the region less safe."

'Maximum restraint'

European and international officials are calling for "maximum restraint."

Pompeo's visit to Central Command is unusual in that he is not accompanying Shanahan. A defense official told CNN that Shahanan is remaining in DC to "continue to develop options." Shanahan was at the White House on Monday, the official said, and is meeting throughout the day Monday and Tuesday with the chairman of the Joint Chiefs of Staff, Gen. Joseph Dunford.

"Right now he needs to stay in DC," the official said.

State Department spokeswoman Morgan Ortagus said Monday that Pompeo will meet with CENTCOM commander Gen. Kenneth McKenzie and Gen. Richard Clarke, the head of Special Operations Command, "to discuss regional security concerns and operations."

President Donald Trump announced May 24 that the Pentagon would be deploying an additional 1,500 troops to the region as a "mostly protective" force.

As tensions intensify, European Union foreign policy chief Federica Mogherini announced Monday that she would travel to Washington for meetings on Tuesday. As she called for calm, she cited Secretary-General of the United Nations António Guterres, who said recently that the world cannot afford another crisis in the Middle East.

"Maximum restraint and wisdom should be applied," Mogherini said.

Apart from the United Kingdom, European governments have not echoed the US claim that Iran was behind the attack on the two tankers. "We have to be very, very careful here," said one European diplomat. "I'm not saying that I don't share their assessment," the diplomat said of the Trump administration, "I'm just saying that so far, we have not decided where we are at, basically, we're still gathering information."

Iran continues to deny US allegations

Iran's ambassador to the UK, Hamid Baeidinejad, denied allegations that Tehran is behind the tanker attack in an exclusive interview with CNN's Christiane Amanpour.

Baeidinejad cautioned the White House would be "very sorry" to underestimate Iran should a military conflict ensue. When asked who else could be responsible for the tanker attack, Baeidinejad pointed to other countries in the region "who have invested heavily, billions and billions of dollars, to draft the United States into a military conflict with Iran."

Saudi Arabia, Iran's regional arch-enemy, has backed and encouraged US steps to confront Iran.

As the US maximum pressure campaign against Iran has intensified, the country's officials have complained that while they have adhered to the nuclear pact, US sanctions mean they have gained none of the promised benefits.

After targeting Iran's oil sector in April, the Trump administration revoked sanctions waivers in May that allowed Iran to comply with nonproliferation elements of the nuclear deal. The waivers had allowed Iran to ship away enriched uranium, keeping it below levels mandated by the deal.

After Pompeo's Sunday remarks about the possible use of military force, Behrouz Kamalvandi, a spokesman for the Iranian atomic agency, said during a Monday news conference that Iran will now accelerate uranium enrichment to 3.7%, above the 3.67% mandated by the nuclear deal.

"If Iran feels that the sanctions have been reinstated or not lifted, Iran has the right to partly or on the whole suspend its commitments" to the pact, Kamalvandi said. He added that there is still time for European countries to save the nuclear deal if they "abide by their commitments."

US allies expressing frustration

Privately, Europeans express frustration with the US approach to Iran, encapsulated by a Pompeo speech laying out 12 ways Iran must change, which many have described as regime change in all but name. "We don't think all of the escalation was necessary," the European diplomat said.

"To be frank, it's very hard to understand what the big picture is or the end game," the diplomat said of the US strategy, noting that the Trump administration has proposed no alternative to the nuclear deal and has so far refused to engage in talks with Tehran.

"Trump wants a better deal, but it's hard for the EU to understand how you're going to get there. We did have a system a few years ago where all the major powers came together to pressure Iran to get the deal we reached," the diplomat said. "That was an enormous effort."

The deal was constructed around "the old stick and carrot idea," the diplomat said. "Now it's just sticks. Where's the carrot? Why should Iran now talk and with what outcome? What's the idea? There don't seem to be any alternatives here. There's no great, grand strategy and that makes it very hard to deal with it."

Guterres and other world leaders reacted to Iran's uranium announcement by urging Tehran to stay the course. The UN secretary-general also urged "all parties to refrain from any steps that may lead to further escalation of tensions in the region," spokesman Stephane Dujarric said Monday.

French President Emmanuel Macron told reporters that he regretted the Iranian announcement and noted that so far they have complied with the nuclear deal. "We encourage them to adopt a patient and responsible behavior," he said.

Pompeo and like-minded allies argued Sunday that the administration is justified in considering a military response to Iran.

"The United States is considering a full range of options," Pompeo said on CBS' "Face the Nation." When asked if a military response was included in that set of actions, Pompeo said, "Of course."

"The President will consider everything we need to do to make sure, right? But what's the President said? We don't want Iran to get a nuclear weapon," Pompeo added. "President Trump has said very clearly, he doesn't want to go to war."

The head of the EU's External Action Service, Helga Schmid, said the risk of miscalculation remains high. Schmid, who has just returned from a June 12-15 trip to the United Arab Emirates, Oman, Qatar and Iran, said the EU was focused on defusing regional tensions and finding ways to promote dialogue.

"The risk of miscalculation remains high, especially in the absence of dialogue," Schmid said in a statement.