Turkmenistan last week held back on approving more than 100 requests from the US embassy in Ashgabat for American citizens in neighbouring Iran to cross the land border into the country, according to an obtained US State Department cable that was circulated to diplomats.

Relations between the US and Turkmenistan are under strain. In early June, the Trump administration announced US entry restrictions on nationals of countries including Turkmenistan, restricting entry to persons assessed as having exceptional circumstances. Turkmenistan on June 10 responded to the announcement with a Foreign Ministry statement that described it as “hasty” and as causing “utter incomprehension and concern”.

The requests to Ashgabat to allow the US citizens in the Islamic Republic of Iran to enter Turkmenistan were submitted in the days ahead of the June 22 US stealth bomber “Midnight Hammer” strikes on Iranian nuclear development sites. Citizens of many other countries have been using a “humanitarian corridor” set up by Turkmenistan to depart Iran since the Israeli-Iranian air war began.

The June 20 cable, which came into the possession of the Washington Post, noted that the US State Department was now advising the US citizens within Iran to find other routes to leave the country, such as land routes via Azerbaijan, Armenia or Turkey.

Following the US bombing of Iranian nuclear facilities, US diplomats appeared to move to shore up relations with Turkmenistan, Iran’s northern neighbour.

US Deputy Secretary of State Christopher Landau initiated a phone call on June 22 with Turkmen Foreign Minister Rashid Meredov. The State Department did not release information about the discussion. However, according to an official Turkmen statement, the talks seemed to focus on the volatile Middle East situation.

The statement said the call occurred in a “friendly and constructive atmosphere”, adding that Turkmenistan’s traditional neutral status was mentioned. It also referred to Ashgabat’s “readiness to participate in resolving the current situation in the Middle East by using the widest range of diplomatic means and methods.”

The internal cable reportedly observed that "numerous" US citizens had faced "delays and harassment" while trying to exit Iran. Without providing further details, it added that one unidentified family had reported that two US citizens attempting to leave Iran had been detained.

How many US citizens are in Iran is unknown, but in the past US officials have estimated the number as in the thousands.

The Islamic Republic treats Iranian-US dual citizens solely as nationals of Iran, the US State Department said in a travel alert.

"U.S. nationals are at significant risk of questioning, arrest and detention in Iran," it advised.