The US has said it is sending an aircraft carrier and a bomber taskforce to the Middle East in response to what it called “a credible threat” by Iranian regime forces.

The deployment of forces was first announced by the national security adviser, John Bolton, on Sunday, and confirmed by the acting defence secretary, Patrick Shanahan, on Monday. Neither official gave an explanation of the alleged Iranian threat. According to one report, information passed on by Israeli intelligence contributed to the US threat assessment.

Shanahan said in a series of tweets on Monday that the deployment “represents a prudent repositioning of assets in response to indications of a credible threat by Iranian regime forces”.

“We call on the Iranian regime to cease all provocation. We will hold the Iranian regime accountable for any attack on US forces or our interests,” he said.

Rotations of US troops and military hardware around the world are routine and usually take place without fanfare. At present there is no aircraft carrier or bomber taskforce in US Central Command’s area of operations, the Middle East and Afghanistan. The Abraham Lincoln carrier strike group is in the Mediterranean and was on the way to the Middle East anyway, but defence officials said its trip would be accelerated. It was unclear on Monday what kind of bombers would be deployed to the region and where they would be based.

The announced deployment comes in the midst of a week of particular high tension. On 2 May, the US ended waivers that allowed China, India and Turkey to continue to buy Iranian oil without US sanctions. Wednesday marks the first anniversary of the US withdrawal from the 2015 nuclear deal with Iran, and both Donald Trump and Hassan Rouhani are expected to mark the day by raising the stakes.

Trump is expected to add more sanctions and Iranian media have reported Rouhani will announce that Iran will stop compliance with elements of the 2015 nuclear deal in response to US violations of the agreement, the Joint Comprehensive Plan of Action (JCPOA).

Asked for clarification on the military deployments on Monday, the US secretary of state, Mike Pompeo, was vague, but suggested the US anticipated a threat from an Iran-backed group in the region.

“I don’t want to talk about what underlays [sic] it, but make no mistake. We have good reason to want to communicate clearly about how the Iranians should understand how we will respond to actions that they may take,” Pompeo told reporters on the way to a meeting of the Arctic Council in Finland.

“It is absolutely the case that we’ve seen escalatory action from the Iranians, and it is equally the case that we will hold the Iranians accountable for attacks on American interests,” he said. Pompeo added that if attacks came from “some third-party proxy, whether that’s a Shia militia group or the Houthis or Hizbullah, we will hold the … Iranian leadership directly accountable for that”.

CNN quoted unnamed officials on Monday as saying there was “specific and credible” intelligence that Iranian forces and proxies were targeting US forces in Syria, Iraq and at sea, with “multiple threads of intelligence about multiple locations”.

Bolton’s declaration came a few days after the Iranian government expressed concern that Bolton and other hawks were seeking to draw the Trump administration into a new war.

In a written statement, Bolton said the ships and planes were intended “to send a clear and unmistakable message to the Iranian regime that any attack on United States interests or on those of our allies will be met with unrelenting force”.

“A carrier into CentCom is not unusual and was likely routine and long planned,” said Ilan Goldenberg, a former state department and Pentagon official, now a senior fellow at the Centre for a New American Security in Washington. “The inflammatory language from Bolton is unusually provocative but my guess is just an opportunity to try to intimidate the Iranians. Nothing more.”

Bolton has been pushing for a tougher stance by the US towards North Korea, Venezuela and Iran. Before taking his White House position, he argued that bombing Iran was the only way to stop it acquiring a nuclear weapon.

During a visit to New York last month, the Iranian foreign minister, Mohammad Javad Zarif, warned that what he called a “B Team” consisting of Bolton, the Israeli prime minister, Benjamin Netanyahu, the Emirati crown prince Mohammed bin Zayed and his Saudi counterpart Mohammed bin Salman, were seeking to goad the US and Iran into a conflict.

“We don’t believe that President Trump wants confrontation. But, we know that there are people who are pushing for one,” Zarif told the CBS programme, Face the Nation. “I think the US administration is putting things in place for accidents to happen. And there has to be extreme vigilance, so that people who are planning this type of accident would not have their way.”

It is unclear how Rouhani will respond. Iranian media are predicting he would announce on Wednesday that Iran no longer feels bound by elements of the JCPOA.

Ali Vaez, an Iran expert at the International Crisis Group, said that Iran had not expected China, India and Turkey to comply with the US-declared oil embargo.

“That was the basis for Tehran’s ‘strategic patience’,” Vaez said, predicting that Rouhani will announced more research and development work on uranium-enriching centrifuges. “Increasingly Iran has less and less to lose.”

That would put European states in a difficult position. The UK, France and Germany are parties to the JCPOA and have insisted they would uphold it, as long as Iran continued to abide by its terms. Experts from Iran, the three European states, Russia and China, are due to meet in Brussels on Tuesday.

“Iran is likely to test the limits of the JCPOA without blowing it up,” Ariane Tabatabai, an associate political scientist at the RAND Corporation. “They want to send a message that will put pressure on the Europeans, but will not make Russia angry.”