A Palestinian-American doctor said he walked out of a Ramadan event with President Joe Biden at the White House to show solidarity with the people of Gaza against Israel's offensive.

Thaer Ahmad, who traveled to Gaza earlier this year, told CNN he left the meeting between Biden and members of the Muslim community on Tuesday in protest at US "rhetoric" supporting Israel.

"I let him know that I am from a community that's reeling. We are grieving. Our heart is broken for what's been taking place over the last six months," Ahmad, an emergency doctor from Chicago, said he told the president.

He said he then "let him know that out of respect for my community, out of respect for all of the people who have suffered, who have been killed in the process, I need to walk out of the meeting."

Biden "actually said that he understood," he added.

The White House said on Wednesday that Biden respected the doctor's stance.

"The president respects any American's right to peacefully protest," Press Secretary Karine Jean-Pierre told a briefing. "He understands that this is a painful moment for many Americans."

Biden had downsized the traditional event to mark the Muslim holy month of Ramadan amid growing domestic anger over his support for Israel's offensive in Gaza following Hamas's October 7 attacks.

Muslim leaders met the president but asked for there to be no fast-breaking dinner, with Biden holding only a small meal separately with Muslim White House staff.

Tensions over Gaza soared further this week after an Israeli air strike killed seven employees of a US-based charity, World Central Kitchen, on Monday.

Biden said on Tuesday he was "outraged" and accused Israel of not doing enough to protect aid workers or civilians, in one of his strongest statements since the war started.

"I think you can sense the frustration in that statement yesterday," US National Security Council spokesman John Kirby told reporters.

But the White House said that Biden continued to support Israel's "right to defend itself" and there were no plans to curb arms deliveries to the key US ally.