Columbus, Ohio: Washington US Democratic presidential frontrunner Joe Biden says that passing a bill explicitly prohibiting discrimination based on sexual orientation or gender identity will be his number one priority if he is elected to the top job.

"I promise you if I am elected president [passing the Equality act] will be the first thing I'll ask to be done," Biden told hundreds of activists in the keynote speech at the Human Rights Campaign's annual fundraiser in Columbus, Ohio on Saturday.

Former vice-president Joe Biden. Credit:AP

In a 30-minute speech, Biden blasted President Donald Trump for "pushing back" on progress in the fight for equal rights in the US, citing his administration's effective ban on transgender people joining the military and his push to allow discrimination at homeless shelters and at medical service providers.

"It's wrong and it is immoral what they're doing," the former vice-president said on the first day of Pride month, calling the fight of the Lesbian, Gay, Transgender, Bisexual and Queer (LGBTQ) community "the civil rights issue of our generation".

The 76-year-old is one of more than 20 candidates vying for the Democratic Party nomination. Biden's long political career and centrist political stance have helped him become a frontrunner in the Democratic primary race.

Pride events are set to take place across the US during June, including marches in major cities. The march in the US capital, Washington, is scheduled for June 8.

DPA