In an eve-of-Thanksgiving address on Wednesday, Joe Biden drew on historic hardships and his deep personal loss to make a passionate appeal for resilience, asking Americans to endure a national holiday amid restrictions on travel and gatherings imposed to fight the pandemic.

“We need to remember, we’re at war with the virus, not with each other,” Biden said from Wilmington, Delaware, where he is continuing transition work before his inauguration as the 46th president in Washington on 20 January.

The tone was in marked contrast to speeches by Donald Trump, who shortly after Biden spoke announced in a tweet that he was giving a full pardon to Michael Flynn, his first national security adviser who had pleaded guilty to lying to the FBI about contacts with a Russian official.

While Trump has allowed the Biden transition to proceed he has not conceded defeat or stopped making baseless claims of electoral fraud.

Echoing previous speeches informed by the historian Jon Meacham, Biden said George Washington’s army marked the day “under extremely harsh conditions and deprivation.

“Lacking food, clothing, shelter, they were preparing to ride out a long, hard winter … In spite of the suffering, they showed reverence and character that was forging the soul of the nation.

Switching from the epic to the personal, Biden remembered his own family’s first Thanksgiving without his wife, Neilia Hunter Biden, and young daughter Naomi, both killed in a car crash in 1972.

“I know this time of year can be especially difficult,” he said.

Out of division, unity,” Biden said.

Nonetheless, in 56 days’ time Biden will replace Trump in office.

Democrats and Republicans in Congress are preparing for Biden to abandon Trump’s state-by-state approach to fighting the pandemic and build a national strategy instead.

Democrats believe a Biden plan should include elements of the House’s $2tn coronavirus aid bill which aims to revive the US economy.

In his speech in Wilmington on Wednesday, Biden hailed “significant record-breaking progress in developing a vaccine” and said the US was “on track for the first immunisations to begin by late December, early January