Kamala Harris has released her medical records, which concluded she is in "excellent health" and fit for the presidency.
Following the disclosure, the Democratic Party's nominee to be the next US president accused Donald Trump of a lack of transparency over not releasing his own health records.
The vice-president also claimed her Republican rival "doesn't want the American people to see whether or not he's fit to become president".
Without revealing Trump's medical records, the former president's team responded by quoting his doctor as saying that he was in "perfect and excellent health".
The Trump campaign said the Republican nominee had a "extremely busy and active campaign schedule" and claimed Harris "does not have the stamina of President Trump".
The trading of barbs came after the White House published a medical report that said Vice-President Harris “possesses the physical and mental resiliency” necessary to serve as president.
Dr Joshua Simmons, a US Army colonel who has been Harris' physician for over three years, wrote that her most recent physical in April was "unremarkable" - adding that she maintains a healthy and active lifestyle.
He also noted she has a family history of colon cancer and suffers from allergies - going on to say she keeps up recommended preventative care, including having colonoscopy and annual mammograms.
Following the release of the medical records, a Harris campaign spokesman said in a post on social media: "your turn, Donald Trump".
Ahead of a campaign event in North Carolina, Harris also sought to cast doubt on her rival's mental acuity and how he "goes off on tangents".
Democrats have been on the attack about the 78-year-old Trump's age and mental fitness, after months of Republicans directing similar criticisms at President Joe Biden before he exited the race.
If elected president again in November, Trump would end his second term as the oldest serving president in US history at 82 - albeit a record that would be shared with Biden, who will be the same age when he leaves office in January.
In response to the pressure from the Harris camp, the Trump's campaign's communications director Steven Cheung said he had "voluntarily released" updates from his personal physician and the doctor who treated him after the assassination attempt against him this summer in Butler, Pennsylvania.
"All have concluded he is in perfect and excellent health to be Commander in Chief," Cheung added.
He also cited a November 2023 medical letter that said Trump's "physical exams were well within the normal range and his cognitive exams were exceptional".
National polls suggest Harris remains slightly ahead of Trump but the numbers in battleground states are extremely close.
