Barca president Joan Laporta has declared Koeman will be in charge next term.
Guardiola told Mundo Deportivo: "I am a good friend of Ronald and I am very happy, and I know it because I spoke with the president and he is convinced of the decision.
"Ronald deserves to have a year with the people in the stadium, the second years are always better than the first, you already know each other, he already has the team more at hand and at times of the year, Barça played very well. They fell at the end when it was close, but he won the Copa and changed to a defence of five.
"They played very and very well, the best in Spain."
On the appointment of Mateu Alemany as sporting director, Guardiola added: "Mateu will do a great job for sure, yesterday I spoke with the president and he is very happy with the work he is doing."
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