US President Barack Obama Thursday urged Americans to open their hearts to refugees in his Thanksgiving message to the nation, likening them to the pilgrims the holiday celebrates. "Nearly four centuries after the Mayflower set sail, the world is still full of pilgrims - men and women who want nothing more than the chance for a safer, better future for themselves and their families," Obama said in his weekly address, referring to the boat on which the first pilgrims reached the New World. "I've been touched by the generosity of the Americans who've written me letters and emails in recent weeks, offering to open their homes to refugees fleeing the brutality of ISIL," Obama said, using an acronym for the Islamic State group. "People should remember that no refugee can enter our borders until they undergo the highest security checks of anyone traveling to the United States," Obama said.