PHILADELPHIA (Reuters) - Democrat Joe Biden would seek to make gun manufacturers more accountable for mass killings and ban assault rifles but would not force owners to sell their existing high-power weapons to the government, under gun control policy his presidential campaign rolled out on Wednesday.

FILE PHOTO: Former Vice President Joe Biden gestures during the 2020 Democratic U.S. presidential debate in Houston, Texas, U.S. September 12, 2019. REUTERS/Mike Blake/File Photo

The former vice president, who leads in most opinion polls in the Democratic race to take on Republican President Donald Trump in the November 2020 election, unveiled his plan to attack gun violence ahead of a forum on the issue in Las Vegas on Wednesday.

The event is expected to attract 10 Democratic candidates, including Biden’s leading rivals, U.S. Senators Elizabeth Warren and Bernie Sanders.

The gun violence forum is being held one day after the second anniversary of the Las Vegas massacre that killed 58 people, the deadliest mass shooting in U.S. history, and after a summer of deadly mass shootings that shook the country.

Biden’s plan includes several elements that have garnered large support from the Democratic field such as strengthening background checks, opening gun manufacturers to civil action and employing “red-flag” laws that allow family members and law enforcement to temporarily take away guns from people who might pose a danger to themselves or the public.

Most, if not all, of the Democratic candidates for president have called for banning assault weapons and high-capacity magazines, but they differ on how to deal with the existing stockpile of those weapons.

Beto O’Rourke, a former Texas congressman seeking the Democratic nomination, said recently he would force gun owners to give up their assault weapons through a mandatory buyback program, an idea that has gained traction in recent weeks as several candidates - such as U.S. Senators Cory Booker and Kamala Harris - said they considered it a good idea but stopped short of endorsing it.

The Biden plan would force owners of assault rifles to register their weapons with the U.S. Bureau of Alcohol, Tobacco and Firearms. If they did not do so, they would have to sell them to the government.

“First things first,” a senior Biden campaign official said when asked about the lack of mandatory assault rifle buybacks. “We have a comprehensive policy to make sure we are dealing with the problem of assault weapons.”

Warren and Sanders have also resisted calls for mandatory buyback programs.

The Biden plan would not require owners of any type of gun to register with the federal government, as some advocates are seeking, but would support state efforts at enacting such requirements.

Biden would spend $900 million to help America’s cities deal with gun violence, strengthen laws that protect women from violent relationships and seek way to curtail online harassment and study its links to violence.