US Secret Service Director Kimberly Cheatle admitted to Congress on Monday that she and her agency failed when a would-be assassin wounded Republican presidential candidate Donald Trump at a July 13 campaign rally in Pennsylvania this week.

"We failed," Cheatle, who faces Republican calls for her removal, said in testimony before the House of Representatives Oversight Committee. "The assassination attempt on former President Donald Trump on July 13th is the most significant operational failure at the Secret Service in decades," Cheatle said.

In the face of Republican claims that the Secret Service denied resources to protect Trump, she said security for the former president had grown ahead of the shooting.

"The level of security provided for the former president increased well before the campaign and has been steadily increasing as threats evolve," Cheatle said.

She added that the Secret Service provided the security sought by the Trump campaign for the rally.

"What I can tell you is that for the event on July 13, the details that were requested, the assets that were requested for that day, were given," Cheatle said.

She declined to answer specific questions about the day's security plan from Republicans and Democrats, saying the matter was being investigated internally.

Monday's hearing marked the first round of congressional oversight of the attempted assassination. On Wednesday, FBI Director Christopher Wray will appear before the House Judiciary Committee. And House Speaker Mike Johnson is also due to unveil a bipartisan task force to serve as a nexus point for House investigations.

Cheatle has resisted calls for her resignation from top Republicans including Johnson and Senate Minority Leader Mitch McConnell.

Republican House Oversight Committee James Comer echoed those calls.

"It is my firm belief, Director Cheatle, that you should resign," the Kentucky Republican told her. "The Secret Service has thousands of employees and a significant budget. But it has now become the face of incompetence." (Reuters)