The 81-year-old approached the podium for his weekly press conference and began speaking about the annual defence funding bill before appearing to lose his train of thought and trailing off with a drawn-out "uh".

He then appeared to stare vacantly into space for around 20 seconds, before his Republican colleagues grabbed his elbows and asked if he wanted to go back to his office.

He did not answer but slowly walked back to his office with an aide and the senator for Wyoming, John Barrasso.

Mr McConnell was out of the Senate - the upper chamber of Congress - for almost six weeks earlier this year after he fell and hit his head after a dinner event at a hotel.

He was in hospital for several days and his officer later said he suffered a concussion and fractured a rib.

His speech has sounded more halting in recent weeks, prompting questions about his health.

Mr McConnell returned to the press conference 12 minutes later to take questions and said he was "fine".

When asked if he is still able to do his job, he said: "Yeah."

Mr McConnell's office declined to say whether he was seen by a doctor after the episode.

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Colleagues 'continue to be concerned'

After the press conference, Mr Barrasso told reporters he "wanted to make sure everything was fine" and so walked Mr McConnell down the hall to his office.

He said he has been concerned since Mr McConnell was injured earlier this year, adding "and I continue to be concerned."

Later on Wednesday Mr McConnell again told reporters he was fine and said President Joe Biden had called him.

"The president called to check up on me, and I told him I got sandbagged," Mr McConnell joked, referring to a quote from Mr Biden after he tripped over a sandbag and fell while onstage at the US Air Force Academy graduation in June.

Trips and falls

Mr McConnell is the longest-serving Senate party leader and was first elected to the Senate in 1984.

He had polio in his childhood and has long acknowledged some difficulty as an adult in climbing stairs.

In addition to his fall in March he also tripped and fell four years ago at his home in Kentucky, causing a shoulder fracture that required surgery.

Many of the top figures in Washington are elderly, with the average age in the Senate above 64 and Mr Biden running for re-election at 80.