All perfect praise be to Allaah, the Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Assuming the state of Ihraam is making one's intention to perform the rituals, and it is not obligatory on the Muslim assuming the state of Ihraam to say, “O Allaah, I am answering your call to perform Hajj,” or, “O Allaah, I am answering your call to perform ‘Umrah.” Indeed, it is only recommended to say that. Therefore, if the pilgrim did not say that, he bears no sin. A pilgrim who intends to perform Tamattu‘ Hajj may say either , “O Allaah, I am answering your call to perform ‘Umrah,” only, or he can say, “O Allaah, I am answering your call to perform ‘Umrah [during the month of Hajj] followed by Hajj.”
Allaah Knows best.