GREENVILLE, MISSISSIPPI (Reuters) - A Mississippi man pleaded guilty in federal court on Friday to attempting to join the Islamic State in Iraq and Syria (ISIS) with his wife last summer.

Muhammad Oda Dakhlalla, 23, and Jaelyn Delshaun Young, 20, were arrested at a Mississippi airport in August 2015, while attempting to board a flight to Turkey, where they believed an ISIS contact would convey them to Syria, according to court documents filed by US prosecutors.

Young, who has not pleaded guilty and is scheduled to go to trial in June, acknowledged her role as the "planner of the expedition" in an incriminating farewell letter, the documents said.

Dakhlalla entered his guilty plea in US District Court for the Northern District of Mississippi, in Greenville.

In exchange for Dakhlalla's guilty plea to a single count of conspiring to provide material support to a designated terrorist organization, which carries a maximum sentence of 20 years in prison, US prosecutors agreed to not press any other charges.

Both Dakhlalla and Young, of Starkville, Mississippi, are US citizens. Young converted to Islam in March 2015, according to the court documents.

Dakhlalla and Young are two of more than 80 individuals whom the United States has charged with ISIS-related crimes since 2013.

Young's Twitter posts about her desire to join ISIS caught the attention of the FBI in May 2015, and an agent posing as an ISIS recruiter began corresponding with her and Dakhlalla.

The couple, who had married in an Islamic marriage but did not get their marriage legally recognised, were motivated to join the group after viewing ISIS executions of people they deemed immoral, and because they perceived the group as "liberators" of parts of Syria and Iraq, according to court records.

Attorneys for the couple said in court that when they were first charged, they had no weapons nor military training and would not pose a threat to others if released on bond.