Secretary of State Mike Pompeo sent a cable to all US missions overseas ordering diplomats not to meet Iranian opposition groups without specific approval because it could undermine the Trump administration’s diplomatic efforts with the Iranian regime, according to a copy of the cable that CNN obtained.

“Many exiled Iranian opposition groups try to engage U.S. officials regularly to gain at least the appearance of tacit support and enhance their visibility and clout. Direct U.S. government engagement with these groups could prove counterproductive to our policy goal of seeking a comprehensive deal with the Iranian regime that addresses its destabilizing behavior,” Pompeo wrote in the cable.

The cable was first reported by Bloomberg.

The cable lists a number of Iranian opposition groups, including Mujahedeen-e-Khalq (MEK) and five other Iranian opposition groups which are off limits without specific approval. John Bolton, President Trump’s former national security adviser, has previously said the MEK is a “viable opposition” to the current Iranian regime.

Last month, Rudy Giuliani, Trump’s personal attorney, met with Iranian opposition groups that are linked to the MEK. Bolton and Giuliani have also given paid speeches on the group’s behalf. During one of those speeches last year, Giuliani called for regime change in Iran.

The MEK, which was previously on a US terrorism list, paid Bolton to give speeches on its behalf and once employed Giuliani.

Pompeo warned that it would be “counterproductive” to engage these groups. He said that some of them have a history of using violence to achieve political objectives and that some of them seem to overthrow the Iranian regime.

Given the escalating tension with Iran in the wake of the strike which killed Qasem Soleimani, the cable sent a clear message that the Trump administration wants to avoid the perception that they are conspiring with groups to push for regime change.

In recent days, Trump administration officials have not laid out any specific steps they are taking to engage in diplomacy with Iran, though they have said that they are willing to do so. Iran, over the last year, has not acted upon any of Trump’s comments saying that he is willing to meet Iranian leadership.

In the cable, Pompeo cited the administration’s willingness to seek a “comprehensive deal” with Iran that covers a range of Iranian activities including “its destabilizing behavior, including its nuclear program, missile program, support for terrorism, and malign regional behavior.”

The State Department has not replied to a request for comment.