US President Barack Obama greets exiled Tibetan spiritual leader the Dalai Lama at the entrance of the Map Room of the White House in Washington DC on 15 June 2016.

US President Barack Obama greets exiled Tibetan spiritual leader the Dalai Lama at the entrance of the Map Room of the White House in Washington DC on 15 June 2016. White House/Pete Souza

US President Barack Obama greets exiled Tibetan spiritual leader the Dalai Lama at the entrance of the Map Room of the White House in Washington DC on 15 June 2016.

US President Barack Obama greets exiled Tibetan spiritual leader the Dalai Lama at the entrance of the Map Room of the White House in Washington DC on 15 June 2016. White House/Pete Souza

US President Barack Obama meets with the Dalai Lama in the Map Room of the White House, Washington DC, on 21 February 2014.

US President Barack Obama meets with the Dalai Lama in the Map Room of the White House, Washington DC, on 21 February 2014. White House/Pete Souza

US President Barack Obama meets with the Dalai Lama in the Map Room of the White House, Washington DC, on 16 July 2011.

US President Barack Obama meets with the Dalai Lama in the Map Room of the White House, Washington DC, on 16 July 2011. White House/Pete Souza

US President Barack Obama meets with the Dalai Lama in the Map Room of the White House, Washington DC, on 18 February 2010.

US President Barack Obama meets with the Dalai Lama in the Map Room of the White House, Washington DC, on 18 February 2010. White House/Pete Souza

US President George W Bush talks with the Dalai Lama before he received the Congressional Gold Medal in the US Capitol Rotunda in Washington, DC, on 17 October 2007 . President Bush participated in the ceremony despite Beijing's strong disapproval of the recognition for the 72-year-old exiled leader from Tibet.

US President George W Bush talks with the Dalai Lama before he received the Congressional Gold Medal in the US Capitol Rotunda in Washington, DC, on 17 October 2007 . President Bush participated in the ceremony despite Beijing's strong disapproval of the recognition for the 72-year-old exiled leader from Tibet. Getty Images/Chip Somodevilla

US President George W Bush wears a scarf that was presented to him by the Dalai Lama in the private residence of the White House in Washington, DC, on 9 November 2005.

US President George W Bush wears a scarf that was presented to him by the Dalai Lama in the private residence of the White House in Washington, DC, on 9 November 2005. White House/Paul Morse

US President George W Bush meets with the Dalai Lama at the White House in Washington DC on 10 September 2003.

US President George W Bush meets with the Dalai Lama at the White House in Washington DC on 10 September 2003. White House/Paul Morse

US President George W Bush meets with the Dalai Lama at the White House in Washington DC on 23 May 2001.

US President George W Bush meets with the Dalai Lama at the White House in Washington DC on 23 May 2001. White House/Eric Draper

US President Bill Clinton meets with the Dalai Lama at the White House in Washington DC on 20 June 2000. The Dalai Lama met with President Clinton and his national security advisor to discuss Tibet.

US President Bill Clinton meets with the Dalai Lama at the White House in Washington DC on 20 June 2000. The Dalai Lama met with President Clinton and his national security advisor to discuss Tibet. White House/Ralph Alswang

US President Bill Clinton listens to the Dalai Lama during a meeting at the White House in Washington DC, on 10 November 1998.

US President Bill Clinton listens to the Dalai Lama during a meeting at the White House in Washington DC, on 10 November 1998. White House

US President Bill Clinton meets with the Dalai Lama at the White House in Washington DC on 23 April 1997.

US President Bill Clinton meets with the Dalai Lama at the White House in Washington DC on 23 April 1997. White House/Richard Ellis

US President Bill Clinton meets with the Dalai Lama at the White House in Washington DC on 27 April 1993. Also seen in the photo are Vice President Al Gore and Special Envoy and ICT Executive Chairman Lodi Gyari.

US President Bill Clinton meets with the Dalai Lama at the White House in Washington DC on 27 April 1993. Also seen in the photo are Vice President Al Gore and Special Envoy and ICT Executive Chairman Lodi Gyari. White House

US President George HW Bush meets with the Dalai Lama at the White House in Washington, DC, on 16 April 1991. It was the first time that a US president meets with the Dalai Lama.

US President George HW Bush meets with the Dalai Lama at the White House in Washington, DC, on 16 April 1991. It was the first time that a US president meets with the Dalai Lama. White House