Manolev said he would never wear the Bulgarian shirt while the German was in charge after he was left out of the squad for Friday's Euro 2012 Group G qualifier against England.
Matthaus said Manolev had been dropped for "not being serious in training" but added that the national team's door was not closed.
"I'll continue playing, of course, I'm Bulgarian after all," Manolev, who had been capped 18 times after making his debut in 2008, told Darik radio. "I will always play for Bulgaria.
"Matthaus told me that I'm not in a good shape and I was very annoyed. I told him that I'm going back to the Netherlands to improve my form.
"But now I can say that Matthaus can always rely on me," added Manolev, who joined PSV Eindhoven from Litex Lovech on a three-year contract in 2009.
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