Martinez has spent much of this season being asked about Barkley's readiness to be part of Roy Hodgson's squad in Brazil this summer.
While he refused to champion the youngster's cause on Tyneside, he insisted he would be ready if Hodgson came calling.
The Spaniard said: "All I can say is that Ross is ready to help the national team, and nothing will faze him.
"If the national team manager believes that he needs the role of Ross, he will be ready; if not, he will have a good summer and he needs to regenerate and recover after what has been his best and most demanding season as a professional.
"I know that Ross Barkley will be a phenomenal footballer for England and English football.
"But the timing has to be measured by the manager in the England set-up and we all have to respect that because every manager prepares a certain squad for different reasons.
"Ross is a proud Evertonian, he loves playing football and is a proud Englishman, and he would be very, very proud to represent England whenever he is called."
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