President Donald Trump’s own top science adviser for COVID-19 vaccine distribution said on Tuesday that he can’t explain Trump’s executive order that purports to put Americans ahead of other countries in getting vaccinated for coronavirus, after reportedly failing to secure doses of the vaccine when made an offer by Pfizer earlier this year.

“Frankly, I don’t know,” Operation Warp Speed chief science adviser Moncef Slaoui said, when asked about an “America First” executive order that Trump said that he would be signing on Tuesday to prioritize Americans ahead of people in other countries who are lining up to get COVID-19 vaccines. Vaccines are already being rolled out to protect against coronavirus in the United Kingdom.

BREAKING: Pressed by @GStephanopoulos to explain Pres. Trump's executive order prioritizing Americans’ access to COVID-19 vaccines before the United States helps other countries, "Operation Warp Speed" Chief Science Adviser Dr. Moncef Slaoui says, "Frankly I don't know." pic.twitter.com/Wk7ElJKDaw

— Good Morning America (@GMA) December 8, 2020

“Frankly, I’m staying out of this, so I can’t comment,” told ABC’s George Stephanopoulos.  When pressed on Trump’s promise, Slaoui said “I literally don’t know,” adding, “I don’t know exactly what this order is about.”

In a separate Fox News interview on Tuesday morning, Slaoui was equally speechless about the order, saying, “what the White House is doing is what the White House is doing.”

The news comes after Pfizer said they were facing supply chain issues that could delay vaccine distribution, in addition to a report from The New York Times that indicated the Trump administration had passed up an opportunity to secure millions of doses of a potential vaccine from Pfizer when an offer was made in July.

The White House is scheduled to host a vaccine summit Tuesday where Trump is anticipated to congratulate Operation Warp Speed officials and others involved in the U.S. vaccine distribution effort in spite of reports that vaccine doses to Americans may lag behind other countries.

Slaoui is the latest to play clean up behind Trump amid the reports, saying that he remains “confident” that his team will be able to secure enough doses to vaccinate against COVID-19 to reach a majority of the population by the middle of next year.

In addition to vaccines advanced by Pfizer and Moderna, Slaoui said that two other vaccine candidates had moved into their third phase of clinical trials and that he is hopeful that pending approval, those vaccines will be available in February to supplement the number of doses that will be available to quickly vaccinate Americans to keep to its promised deadline.

“We’re still on track,” Slaoui said.