After two attempted assassinations and an ongoing threat from Iran, Donald Trump’s campaign has ramped up requests for security, including transport by military aircraft and additional security measures on the ground at the former president’s campaign stops, three sources familiar with the discussions told CNN.

Trump’s campaign wants to use these resources – including access to military aircraft with deterrent systems to protect against surface-to-air missiles – as the former president crisscrosses the US during the final weeks of the presidential campaign.

President Joe Biden, when asked about Trump’s requests on Friday, said they should be fulfilled – “as long as he doesn’t ask for F-15s.”

“I’ve told the department to give him every single thing he needs … as he were a sitting president,” Biden said. “If it fits into that category, that’s fine.”

Susie Wiles, co-campaign manager for Trump, initially made the request for enhanced measures during a call about two weeks ago with Biden’s chief of staff, Jeff Zients, two sources familiar with the conversation told CNN. Wiles then made the formal request for additional security with acting Secret Service Director Ronald Rowe on September 30, according to an email reviewed by CNN.

A third source familiar with Wiles’ call with Zients said Biden’s chief of staff immediately connected Wiles to leadership at the Department of Homeland Security and Secret Service “so she had a direct line.” The source said Zients made clear that the president had directed the Secret Service to provide the highest level of protection for Trump.

The requests from Trump’s campaign also include access to Camp David vehicles for Trump’s primary motorcade as well as access to other military assets, such as drones with thermal monitoring.

In addition, Trump’s campaign asked the US Secret Service to increase stockpiles of ballistic glass across several key swing states that the agency now uses to encase Trump at his outdoor rallies.

And the campaign asked for more funding for local law enforcement officials who augment the president’s security detail and for additional administrative support from Secret Service headquarters.

The Secret Service is now working on formal requests for these resources that will first go to the Department of Homeland Security and then to the Department of Defense as well as any other agencies that would need to be involved, according to a federal law enforcement official.

Two sources close to the campaign said Trump officials are frustrated that the extra protections have not been implemented given the heightened security threats facing the former president, and the campaign has begun implementing some new security measures.

According to one of the sources, Trump has started changing up his routine, taking different planes to events around the country and staying at different properties than he usually would as the 2024 presidential election nears.

The source said Trump’s security team implemented the changes because it had lost faith in the Secret Service following the two attempts on the former president’s life as well as the denial of certain resources in the past. Trump’s team maintains that its concerns are with those at the Secret Service headquarters, not with Trump’s personal detail, many of whom have been with the former president since he left office.

But Trump’s team has also been informed that some of the requests aren’t feasible for any presidential candidate. Trump has complained privately that he is forced to hold smaller rallies because of the security concerns, though every president and presidential candidate has faced restrictions on their freedom of movement because of security concerns, according to two sources familiar with the matter.

Security resources are also often determined on a case-by-case basis, one administration official said.

The Secret Service maintains that “the former president is receiving the highest levels of protection,” agency spokesman Anthony Guglielmi said in a statement Friday. “The Secret Service will remain vigilant and continue to adjust and enhance its protective posture as needed to mitigate evolving threats.”

Guglielmi said the agency is already imposing flight restrictions over Trump’s residence and when he travels. Guglielmi also said that the former president “is receiving the highest level of technical security assets which include unmanned aerial vehicles, counter unmanned aerial surveillance systems, ballistics and other advanced technology systems.”

Still, the request for additional resources could hit roadblocks. Some of them may run into legal issues given constitutional limits on the military operating inside the United States, the federal law enforcement official said.

The Secret Service has implemented a number of changes since Trump was nearly killed by a shooter in July and after another shooter allegedly set up what prosecutors called a “sniper’s nest” outside Trump’s Florida golf course in September when the former president was playing just one hole away. Separately, US authorities have obtained intelligence showing that there is an Iranian assassination threat against Trump.

The Secret Service has increased its presence around Trump, adding members to his detail and taking extra precautions, often traveling with a counter assault team. Secret Service agents previously assigned to desk jobs or other posts also have also been brought into the rotation to protect Trump.

After Trump’s near-assassination in Pennsylvania in July, the campaign also requested that it be allowed to have an observer in command centers with local, state and federal authorities during campaign events, a source familiar with the ask told CNN. This individual would be privy to law enforcement communications and have a direct line of contact with senior campaign officials.

This story has been updated with additional information.