The U.S. Conference of Mayors on Tuesday passed resolutions calling for more gun control, including limits on the number of guns a person may purchase in a single transaction.

The conference, a bipartisan organization of mayors representing cities with more than 30,000 people, passed the resolutions at their annual meeting in Boston, Mass.

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The mayors called for a ban on military-style assault weapons, such as AK-47s, and large-capacity ammunition-feeding devices.

They also oppose proposals to arm teachers and other non-law enforcement officials, which has been pushed by President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE.

The age to purchase a gun should also be raised to 21, the mayors said, and juveniles should be banned from possessing semiautomatic assault rifles.

The resolution mentioned the school shooting at Marjory Stoneman Douglas High School in Parkland, Fla., where a semiautomatic rifle was used to kill 17 people.

"The U.S. Conference of Mayors stands with the students from Marjory Stoneman Douglas High School and all other young people and adults committed to seeing reasonable gun safety policies and to reducing gun violence in our cities," the mayors said.

The mayors also called for comprehensive background checks and bans on bump stocks sales.

They also urged Congress to pass legislation that would allow family members and law enforcement to seek court permission to temporarily remove funs from a person in crisis.

Trump said after the Parkland shooting that he would push for comprehensive background checks and a ban on bump stocks, but those proposals have seen little action.