Iran boss Carlos Queiroz has accused his South Korea counterpart Choi Kang-hee of "humiliating" the Iranian people by claiming he and his players had been "badly treated" in Tehran last year.
Choi said he had suffered poor hospitality and bad manners when he took his side to the Iranian capital for a 1-0 World Cup qualifying defeat in October.
And with the two sides meeting again in a crucial Group A game in Ulsan on Tuesday - the Koreans top the group, with Iran a point behind and with a poorer goal difference - the South Korea coach said he wanted to stop the Iranians from qualifying for Brazil.
He said he would prefer it if third-placed Uzbekistan qualified instead, sparking an irate reaction from Queiroz.
The Portuguese denied that hospitality in Tehran had been poor and told reporters: "Choi should apologise to the Iranian people.
"He said the Korean team was badly treated in Iran - but we gave them the best treatment available. He humiliated the Iranian citizens."
The situation in Group A means a draw on Tuesday would secure automatic qualification for both teams unless Uzbekistan can rack up a big win over Qatar.
And mindful of the impact that goal difference could still have on the group, Quieroz accused South Korea of not maintaining their momentum in their 4-2 win over the Uzbeks on Friday.
He claimed: "South Korea did not do its best in the game against Uzbekistan. I will buy an Uzbek uniform and give it to Choi as a present."