Haley next to Trump when she was Washington's ambassador to the United Nations during his presidency (Reuters)

US Republican Party presidential candidate Nikki Haley questioned the mental competency of her rival, former President Donald Trump, after he accused her, in a slip of the tongue, of failing to stop the attack on the Congress building 3 years ago.

Haley denied that she had taken charge of security in the Congress building at the time, and explained that she was not in her current position at the time. She said in front of a rally in New Hampshire: “They say he was confused, and he was talking about something else.”

The former US ambassador to the United Nations and governor of South Carolina added: "My concern is that I'm not saying anything offensive, but when you're dealing with the pressures of the presidency, we can't have another person questioning whether they're mentally competent to do this."

During a campaign event in New Hampshire last Friday, Trump mixed up Nikki Haley with House Speaker Nancy Pelosi when he addressed responsibility for the events at the Capitol, saying that Haley rejected an offer of assistance while the building was under siege.

The House of Representatives committee that investigated the events of January 6, 2021 said that it found no evidence that he made such an offer.

Trump and other Republicans have repeatedly raised questions about whether 81-year-old President Joe Biden has the mental competency necessary for a second term.

But Haley's comments, who turned 52 on Saturday, were the most direct from a Republican Party official about the mental competency of the 77-year-old Trump.

Critics say Trump is increasingly showing signs of aging.

When asked earlier this week about the matter, the former president repeated the story of how he "excelled" a visual acuity test by correctly identifying animals such as a giraffe, a tiger and a whale from a distance.

Despite these and other criticisms, Trump remains the most likely candidate among Republicans so far.

Source: Al Jazeera + agencies