By Francois Murphy

VIENNA, May 28 (Reuters) - The trial of a 21-year-old man over a foiled Islamist attack on a Taylor Swift concert in Vienna in 2024 enters its final day on Thursday, with the defendant, Beran A, having already pleaded guilty to the main charges including terrorism-related offences.

Beran A, whose last name has not been made public in accordance with Austrian privacy rules, was arrested on August 7, 2024, the day before the first of three planned concerts by the U.S. pop star in the Austrian capital.

All three dates were then cancelled, to the dismay of fans and of Swift, who wrote afterwards that it was "devastating."

Beran A, who is Austrian, has pleaded guilty to charges related to the planned attack, which carry a maximum sentence of 20 years in prison.

Prosecutors say he tried but failed to illegally buy weapons including a machine gun and hand grenade, and followed instructions in an Islamic State video posted online to make a small amount of the explosive triacetone triperoxide (TATP).

He is also accused at the same trial of plotting separately with two school friends to carry out a solo attack each earlier in 2024 in separate Middle Eastern cities. He and co-defendant Arda K admit they travelled to Dubai and Istanbul respectively to carry out attacks but then did not follow through.

They deny, however, providing moral support to the third man, who was arrested in Mecca on suspicion of stabbing a security official at the holy city's Grand Mosque. He is still in custody in Saudi Arabia.

Thursday's court proceedings in Wiener Neustadt, a town near Vienna, are due to begin at 9 a.m. (0700 GMT). The prosecution and defence will make their closing arguments before the jury retreats to deliberate. A ruling is expected later on Thursday.

(Reporting by Francois Murphy in Vienna;Editing by Matthew Lewis)