Iran has declared it “will not wage war against any nation” after the US announced that a further 1,000 troops are to be sent to the Middle East amid rising tensions.

The US move, announced by the acting defence secretary, Patrick Shanahan, comes after the US blamed Iran for attacks on two oil tanker ships last week, which has raised fears of a confrontation, and Tehran declaring it had increased its rate of uranium enrichment.

Shanahan said the troop deployment was for “defensive purposes”, citing concerns about a threat from Iran. “The recent Iranian attacks validate the reliable, credible intelligence we have received on hostile behaviour by Iranian forces and their proxy groups that threaten United States personnel and interests across the region,” he said in a statement.

The Iranian president, Hassan Rouhani, replied on Tuesday that Iran had no desire for conflict.

“Iran will not wage war against any nation,” Rouhani said in a speech broadcast live on state TV. “Those facing us are a group of politicians with little experience.”

He added: “Despite all of the Americans’ efforts in the region and their desire to cut off our ties with all of the world and their desire to keep Iran secluded, they have been unsuccessful.”

The US released more photographs on Monday to support its claims that Iran was responsible for attacks on commercial tankers in the Gulf of Oman.

One of the pictures appeared to show in colour and sharper focus an incident that had previously been presented in a grainy black and white video – a patrol boat with black-uniformed sailors alongside one of the tankers, the Kokuka Courageous.

A statement accompanying the images said the incident was filmed from a US helicopter and occurred after blasts had hobbled the two ships on 13 June. The crew of the Kokuka Courageous had spotted an unexploded mine on the hull and abandoned ship.

“Later that day, an Islamic Revolutionary Guard Corps (IRGC) Gashti Class patrol boat approached Kokuka Courageous and was observed and recorded by a US navy MH-60R helicopter removing the unexploded limpet mine from Kokuka Courageous,” said the statement issued by US Central Command.

“Iran is responsible for the attack based on video evidence and the resources and proficiency needed to quickly remove the unexploded limpet mine.”

The statement does not make any claim on why the Iranians removed the mine, for example in an attempt to remove evidence.

The US has not presented any evidence of mines being attached, and the head of the company operating the Kokuka Courageous, Yukata Katada, has said the crew had reported that the ship was attacked by a “flying object”.

On Tuesday, the US secretary of state, Mike Pompeo, is also due to visit the Florida headquarters of US Central Command (in charge of all operations in the Middle East) and US special forces.

It is unusual for a secretary of state to visit military headquarters, especially as the acting defence secretary is reported to be staying in Washington. Pompeo has taken the lead role in the administration’s campaign of “maximum pressure” on Iran, since the US withdrawal from a multilateral nuclear deal in May last year.

Tehran on Monday announced it would soon breach limits on how much enriched uranium it can stockpile under the nuclear deal.

The accord, which was brokered by Barack Obama and which Iran and the other signatories have maintained following Trump’s withdrawal, caps Iran’s stock of low-enriched uranium at 300kg enriched to 3.67%. But Iran said it had quadrupled the rate of enrichment, so that in 10 days it would bypass the 300kg limit.

A spokesman for the White House national security council said this amounted to “nuclear blackmail”.

Morgan Ortagus, a spokeswoman for the state department, told reporters on Monday: “We continue to call on the Iranian regime not to obtain a nuclear weapon, to abide by their commitments to the international community.

“It’s unfortunate that they have made this announcement today. It doesn’t surprise anybody and this is why the president has often said that the JCPOA [joint comprehensive plan of action] needs to be replaced with a better deal.”

The US decision to pull out, and Trump’s “America first” approach to foreign policy, appears to have damaged trust with allies, some of whom are seeking stronger proof that Iran was behind the oil tanker attacks.

Critics accuse the Trump administration of manufacturing a crisis. Ben Rhodes, former national security adviser to Barack Obama, tweeted: “Trump pulling out of the Iran deal has led directly and predictably to the Iranian nuclear threat getting worse and the risk of war going up.”

On Tuesday, China urged restraint, saying the US risked “opening a Pandora’s box” in the Middle East.

State councillor Wang Yi said “the US side should alter its extreme pressure methods. Any unilateral behaviour has no basis in international law,” and warned it could create “an even greater crisis”. Wang also urged Iran not to abandon the nuclear deal.