WASHINGTON (Reuters) - U.S. law enforcement agencies are working to ensure security at the Republican Party's convention in Milwaukee this week, following an assassination attempt on Donald Trump at a campaign rally.

Trump escaped with minor injuries and will accept the formal Republican presidential nomination at the four-day convention, expected to draw more than 50,000 people.

"We feel very comfortable that we're working with the Secret Service. We're working with 40 different law enforcement agencies in terms of what that security is going to look like," Republican National Committee Chair Michael Whatley said in an interview on Fox.

Trump, 78, had just begun to speak in Butler, Pennsylvania, on Saturday evening when a bullet pierced his right ear, streaking his face with blood.

A 50-year-old volunteer firefighter died shielding his family to protect them from the bullets. Two other rally attendees were critically wounded. Law enforcement agents killed the suspected gunman, a 20-year-old resident of Bethel Park, about an hour away from the rally.

Whatley urged Republicans to use this moment as an opportunity for unity, moving beyond partisan divisions.

"There is no place in politics in any way, shape or form for this kind of violence, for these types of actions. It's a horrific act," Whatley said. "Everybody in America needs to stop. They need to pause, they need to reflect on what is actually important for us in this political process going forward."

Senator Chris Coons of Delaware, who is a key ally for Trump's rival President Joe Biden, said the violence against Trump should motivate both parties to shore up security, with Democrats due to hold their convention in Chicago in August.

"We need to be more concerned and more diligent than ever in ensuring that our two conventions and the rest of this presidential campaign comes off safely and securely," he told NBC.

The Republican convention in Milwaukee this week is set to take place in the arena that is home to the NBA Milwaukee Bucks basketball team.

(Reporting by Katharine Jackson; Editing by Rami Ayyub and Lisa Shumaker)

By Katharine Jackson