Nico-Jan Hoogma, director for the Royal Dutch Football Association, revealed the existence of such a clause last month.
Koeman won four Spanish La Liga titles and one European Cup with the Blaugrana during a six-year spell as a player and has been touted as a potential replacement for the under-fire Ernesto Valverde.
Valverde’s contract with Barcelona expires at the end of this season but he has the option to extend it for a further year.
Koeman is on the verge on qualifying Netherlands for EURO 2020 after the Oranje failed to make it to EURO 2016 and last year’s FIFA World Cup in Russia.
The 56-year-old former Southampton and Everton manager says he is no rush regarding a resolution to his immediate future.
"It's only about Barcelona and also about a time after the European Championship," Koeman told Fox Sports Netherlands when asked about the contract.
"I'm not leaving now, that's 100 per cent certain.
"I think that as a national coach you are entering a process and that takes two years. After the European Championship there is an evaluation moment and who knows, the KNVB may say: 'We have performed so badly at the European Championship, we are not going any further.' Then we will not go further.
"But I have the opportunity to leave for one club, and there is only one club in it.
"I can safely say that I will not leave the Dutch national team for anyone else. I have said often enough that [Barcelona] is my dream club."
