* International affair: The opening parade of last year's Eisteddfod.
The Llangollen International Musical Eisteddfod is writing to Home Secretary Theresa May to ask her to intervene personally to sort out a visa problem caused by a mistake made by one of her officials.
Some performers from Africa and Asia have been refused visas and will not be able to compete at the Eisteddfod in three weeks' time unless Mrs May is able to sort the mess out.
The problem has arisen because the festival has mistakenly been left off a list of so-called "permit-free" festivals so visa applications take more time to process.
Eisteddfod Chair Gethin Davies said: "We have over the years had some problems with visas.
"We had understood that this year we were going to be placed on the permit free list, which is a list of existing 44 festivals, and we thought we were on that list as well, in which case the issue of visas s far more straight forward.
"Due to an administrative oversight at the Home Office which they have held their hands up to, we’re not on that list and consequently each visa application has to be carefully scrutinised by the relevant authorities in the various countries, and some of them are being refused, and it causes us great anxiety.
“In the first place we need a cast iron guarantee that the Llangollen International Musical Eisteddfod will be on the permit free list from now on, plus we want practical help in the short term to assist those people who are still waiting for their visas and to possibly overturn decisions that have been made to refuse other competitors.
"I shall be writing a personal letter to the Home Secretary asking her if she can intervene directly in this, and use her considerable influence to see if this unfortunate state of affairs can be addressed as a matter of urgency.
"The Eisteddfod is on in three weeks’ time, and time is very short, so we are hoping that we can get that help from the highest level, which will enable these wonderful people who want nothing more than to come and share their culture with us in Llangollen so that they will be able to be with us.”
The Home Office have apologised for their error in a letter to Eisteddfod officials.
The letter said: "Unfortunately, due to an administrative oversight on our part when changes to the Immigration Rules were laid in February the Llangollen International Musical Eisteddfod was omitted from the list of permit free festivals included in the new simplified visitor rules.
"I apologise for any inconvenience this will cause however I want to assure you that there are alternative routes that can be used in the meantime."
The iconic event was started in Llangollen in 1947 in the aftermath of the Second World War in an attempt to bring peace and harmony to the world through music and dance.
According to the Eisteddfod, several people from China, Algeria, Tanzania and Ivory Coast had already had their visa applications turned down.
Around 100 dancers and musicians are waiting to hear if they will be granted visas in time to compete at this year's event from 7 July.
Among them are two groups from India, five different groups from Morocco, 14 dancers from Ghana and five from Nepal.
Competitors from other parts of the world outside Africa and Asia are unaffected.
The case has also been taken up by Clwyd South MP Susan Elan Jones.
She said: "The Eisteddfod is hugely important to our area. The Home Office has admitted it has made a mistake and it's now vital they put things right."