The US Defense Department will provide "protective support" to major presidential and vice presidential candidates, increasing its assistance to the country's Secret Service, the Pentagon said on Thursday.

The announcement comes after a gunman lightly wounded Republican candidate Donald Trump and killed a campaign rally attendee last month -- a major failing in Secret Service protection.

"The Department of Defense will provide protective support" until the election in November and likely through the presidential inauguration in January 2025, Deputy Pentagon Press Secretary Sabrina Singh told journalists.

US defense chief Lloyd Austin approved a request from Homeland Security for the assistance, directing the military command responsible for North America to give additional backing to the Secret Service at locations across the country, Singh said.

Trump was wounded in the right ear at a July 13 campaign rally in Pennsylvania by a shooter who was subsequently killed by a Secret Service countersniper.

Secret Service director Kimberly Cheatle resigned in July after acknowledging that the agency had failed in its mission to prevent the assassination attempt, while US media reported earlier this month that multiple agents had been placed on leave.