Activists from around the world have gathered in New York's Greenwich Village to celebrate the 50th anniversary of the birth of the LGBT movement and decry a wave of Trump administration policies they view as a setback for their cause.

Key points: LGBT people and allies will take part in multiple parades and events over the weekend to commemorate the 50th anniversary of the Stonewall Inn riots

LGBT people and allies will take part in multiple parades and events over the weekend to commemorate the 50th anniversary of the Stonewall Inn riots President Donald Trump recently banned transgender people from serving in the military and has cut funding for HIV/AIDS research

President Donald Trump recently banned transgender people from serving in the military and has cut funding for HIV/AIDS research LGBT activists are concerned about the increase in murders of trans women, especially women of colour

The anniversary marks the moment on June 28, 1969, when patrons of Greenwich Village gay bar, the Stonewall Inn, rose up in defiance of police harassment. The unrest triggered a national and global movement for equal rights for lesbian, gay, bisexual, transgender and other queer people.

While the anniversary had a celebratory atmosphere, activists viewed the occasion as an opportunity to protest against US President Donald Trump's record, which many consider to be hostile to LGBT people.

They also wanted to highlight the still-precarious position of LGBT people in many parts of the world.

The original Stonewall Inn didn't survive the 1969 police raid and riots but the current version will be a focal point of this week's celebrations. ( AP: Bebeto Matthews )

"It's always a good time to protest," Lisa Cannistraci, activist and owner of the New York lesbian bar Henrietta Hudson, said.

"Trump got elected and it was devastating for the country, [but] there is a huge silver lining, and that is people are paying attention."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 10 minutes 16 seconds 10 m Stonewall at 50

Between four and six million people are expected to take part in the city's Pride Rally this weekend, which is part of a month-long Pride celebration commemorating the Stonewall uprising.

Mayor of New York Bill de Blasio addressed the gathered crowd.

"I am the Mayor of the largest LGBT community on the face of the Earth and I am proud of that, we are proud of that in New York city," he said.

"We have proven that when you give rights to more and more people everyone benefits, when you respect more and more people the whole community gets stronger."

Lady Gaga, the Grammy Award-winning singer whose signature song Born This Way has become an LGBTQ anthem, fired up the crowd, which began gathering in the park and public square outside the Stonewall early on Friday.

Appearing with a rainbow-coloured jacket and thigh-high boots, she declared that Stonewall was the moment when LGBTQ people said "enough is enough".

"I may not, to some people, be considered a part of this community, even though I like girls sometimes. I would never degrade the fight you have endured," she told the cheering crowd.

"You have the power. You are so, so powerful, and I hope you feel that power today."

Lady Gaga joined Whoopi Goldberg, Alicia Keys and drag performers at the Pride Live's Stonewall Day concert. ( Ap: Greg Allen/ New Yotrk )

Many LGBT activists have fiercely opposed a series of Trump administration initiatives, including a ban on transgender people in the military, cuts in HIV/AIDS research and support for so-called religious freedom initiatives that eliminate LGBT protections.

The White House said Mr Trump had long advocated LGBT equality, noting this year he became the first Republican president to recognise Pride Month and he had backed a global campaign to decriminalise homosexuality.

"President Trump has never considered LGBT Americans second-class citizens and has opposed discrimination of any kind against them," White House spokesman Judd Deere said in a statement.

New York will host two LBGT Pride parades on Sunday to cap off Pride month. ( AP: Frank Franklin II )

The message has been lost on many LGBT people, as the Trump administration opposed extending anti-discrimination protection to gay or transgender workers under federal employment law, a legal issue currently before the US Supreme Court, with a ruling due within a year.

Elle Hearns, a black transgender woman who runs the Marsh P. Johnson Institute promoting trans human rights, said trans people also felt distanced from the corporate sponsorship of Pride events, especially when those same corporations supported other Trump policies and allies.

"There are literally black trans women being murdered across the country in poor, ravaged ghettos that these corporations have done nothing to invest any money in but have certainly encouraged gentrification. It's left the community destitute," Ms Hearns said.

At least 10 transgender people have been murdered in the United States in 2019 after 26 were killed in 2018 and 29 in 2017, according to Human Rights Campaign. Nearly all were trans women of colour.

Reuters/wires