President Donald Trump turned the quirky annual White House ritual of pardoning Thanksgiving turkeys into a riff on his impeachment Tuesday, joking that the two birds had been subpoenaed to testify.

"They've already received subpoenas to appear in Adam Schiff's basement on Thursday," Trump told guests in the Rose Garden, referring to the head of the intelligence committee leading the impeachment probe in the House of Representatives.

Trump was presiding over a ceremony where the president symbolically spares a specially chosen turkey from joining the more than 45 million estimated to be consumed nationwide at Thursday's Thanksgiving holiday.

After online polls were open for 24 hours, a large white bird named Butter won a close vote over his competitor, Bread. Both will be sent to a site known as Gobbler's Rest at Virginia Tech university.

"Butter, I wish you a lot of luck. I hereby grant you a full and complete pardon," Trump said.

He ignored a shouted question from a journalist about whether he planned to use his constitutional power to pardon any of his associates convicted in a series of scandals during his presidency.

Trump also managed to get in a dig at the media, which he almost daily berates as fake, saying journalists would like Tuesday's story because "turkeys are closely related to vultures."