When is it permissible to change the intention from tamattu' to qiran?

Question:
If one intends tamattu', can he change it to qiran?

Answer:
If he has the sacrificial animal with him, he changes it to qiran. If he does not have a sacrificial animal, the Sunnah is that he performs tawaf, sa'y, shortens his hair, and exits the state of ihram, and he does not change it. This is the Sunnah: if he called out the talbiyah for 'Umrah, he performs tawaf, sa'y, shortens his hair, and exits the state of ihram. And if he called out the talbiyah for Hajj, the Sunnah is that he makes it an 'Umrah as well, even if he called out the talbiyah for Hajj, he breaks it off to make it an 'Umrah, performs tawaf, sa'y, shortens his hair, makes it an 'Umrah, and exits the state of ihram, as the Prophet (peace and blessings be upon him) commanded the Companions to do so, except for those who brought the sacrificial animal; whoever has camels, or cattle, or sheep with him, he enters the state of ihram for both Hajj and 'Umrah and does not exit the state of ihram except on the days of sacrifice, and he exits the state of ihram from his Hajj or his 'Umrah.
(Lectures on the Explanation of Bulugh al-Maram, Book of Hajj and 'Umrah)