England caretaker coach Lee Carsley has included the midfielder in his squad for their Nations League qualifiers next week.
Grealish, 29, has not featured for City since October 20 at Wolves.
“National teams always play in this period and I’m always pleased for players to go – when they are fit and they haven’t struggled for the past one, two, three or four weeks,” said Guardiola.
“In 17 days he didn’t train once. Today was the first training and he trained for 20 minutes. That is the reality.
“Yes, he was in the gym for a few minutes for the past two days but it’s a question for the manager from the UK (England) – I’m not involved.”
Guardiola added: “They can select who they want. Jack has had two or three setbacks in terms of injuries and could not get his rhythm.”