TEHRAN, Iran, (AP) – Iran will make the United States “regret” its detention of five Iranian officials in Iraq, Foreign Minister Manouchehr Mottaki said Tuesday.

Mottaki was referring to five Iranian officials detained in the northern Iraqi city of Irbil by U.S. troops in January, who still remain in U.S. custody. The U.S. military has said they are suspected of links to a network supplying arms to Iraqi insurgents — an accusation that Iran has denied.

“We will make the Americans regret their ugly and illegal act,” Mottaki was quoted by the official IRNA news agency as saying. He didn’t elaborate on how Iran will make Washington regret the action.

Iran claimed the men were diplomats and that the building U.S. troops occupied was a government liaison office. It also says the five were the guests of the Iraqi government and has demanded their release. Iraqi government officials have also called for their release, along with compensation for damages.

Unconfirmed reports say the five included the operations chief and other members of Iran’s elite Quds Force, which is accused of arming and training Iraqi militants.

The five have not been charged with a crime. The United States has allowed the International Committee of the Red Cross to visit the men but has so far not allowed Iranian representatives to visit them.

Mottaki said Iran will send a formal letter to the U.N. Secretary General Ban Ki-moon within the next few days to protest inaction by the Security Council and delays in taking up the issue of the five Iranians’ detention.