US President Barack Obama and the Dalai Lama exchanged greetings but did not meet directly at a religious event in Washington closely watched by Beijing, which has warned against any meetings with Tibet's exiled spiritual leader.

Both figures were at an annual prayer breakfast in Washington on Thursday (February 5) where Obama spoke about the importance of religious freedom. The Dalai Lama also attended, seated at a table in the front row across from the president.

Obama nodded and smiled at the Dalai Lama, waving after clasping his hands together in a bow-like gesture toward the Buddhist monk as the event began. Organizers also recognized the spiritual leader, prompting applause.

Senior Obama adviser Valerie Jarrett was seated at the table with the Dalai Lama, a sign of White House support for his presence.

The exchange may still rile China, which bristles at politicians meeting with the Dalai Lama. After the breakfast event was announced, Beijing said it opposed any country meeting with him under any circumstances.

In the wide-ranging speech, Obama also said Islamic State was a "brutal, vicious death cult" that was carrying out "unspeakable acts of barbarism" in the name of religion.

"We have seen violence and terror perpetrated by those who profess to stand up for their faith. Profess to stand up for Islam but in fact are betraying it," Obama said.

Obama said recent acts of violence in Paris, Pakistan and other places across the world show that faith and religion can be twisted to be used as a weapon.