President Joe Biden participated in a climate summit panel in Glascow on Tuesday but was conspicuously absent for the first 20 minutes of his event.

The moderator of the climate forum began by introducing Biden and several other leaders, including United Kingdom Prime Minister Boris Johnson, India Prime Minister Narendra Modi, President of the European Commission Ursula von der Leyen, and President Uhuru Kenyatta.

But Biden did not appear on stage when he was introduced to join the other leaders, who were present at the table as the forum began.

The White House did not offer an explanation for his initial absence.

Biden was not present in the room as Prime Minister Johnson and Prime Minister Modi delivered their remarks, as his chair sat empty for the first 20 minutes of the program.

The president only appeared from behind the stage curtain after the moderator of the forum noted that it was his turn to speak.

Joe Biden appears at a climate summit in Glasgow, Scotland

The president spoke for approximately six minutes about the importance of innovation to deliver a more green economy.

After his speech, Biden joined his fellow leaders at the table, staying seated for the remaining 28 minutes of the event. During the ensuing speeches, Biden was spotted rubbing his eyes, but he remained awake for the rest of the event, unlike at a meeting on Monday, when he fell asleep.

President Joe Biden listens to the speakers during the World Leaders’ Summit “Accelerating Clean Technology Innovation and Deployment” session on day three of COP26 on November 02, 2021 in Glasgow, Scotland. COP26 is the 2021 climate summit in Glasgow. (Photo by Ian Forsyth/Getty Images)

The entire climate event was about 48 minutes, but Biden’s tardiness caused him to miss nearly the first half while he was backstage.

President Joe Biden walks off after speaking during an event about the “Global Methane Pledge” at the COP26 U.N. Climate Summit, Tuesday, Nov. 2, 2021, in Glasgow, Scotland, as John Kerry, United States Special Presidential Envoy for Climate is seen taking the podium, as shown on the screen. (AP Photo/Evan Vucci)

After the event, he stood up and spoke briefly with the other panelists before exiting the stage.