Taoiseach (Irish PM) Micheál Martin has tested positive for Covid-19 on the eve of the St Patrick's Day celebrations in the White House.

He was informed of the positive test while attending the Ireland Fund dinner in Washington.

At the time he was sitting alongside House of Representatives Speaker Nancy Pelosi and other guests.

The taoiseach had been due to receive an international leadership award at the event.

However, when the moment arrived Irish Ambassador to the US, Dan Mulhall, took to the stage and confirmed the positive test.

He said Mr Martin had tested negative but then was re-tested after a member of his delegation received a positive result.

He said the taoiseach had re-tested out of an "abundance of caution" and added that he was in "good form" but very disappointed.

"It is a sad thing which I have to do which is to deliver the taoiseach's speech on his behalf," he said.

The news has cast doubt over the St Patrick's Day celebrations in the White House later.

The taoiseach was due to hold talks with President Biden and take part in the traditional shamrock handover ceremony in the Oval Office.

It is thought the engagements involving President Biden will now be virtual.

Social Democratic and Labour Party (SDLP) leader Colum Eastwood, who was at the dinner, said it was a big blow for the taoiseach.

"It is very sad. This is a major event for any taoiseach, going into the White House on St Patrick's Day, and that now won't happen. I feel very sorry for him," he said

He said the news had left everyone "deflated" at the dinner and with the taoiseach's office due to be rotated later this year, he said Mr Martin would not get another chance to celebrate St Patrick's Day in the White House.

It's not often a taoiseach upstages a US president, but that's what happened last night.

About 700 people gathered for the Washington dinner, with Micheál Martin sitting front and centre beside Mrs Pelosi.

Then it came to the moment he was due to pick up his international award, and it was announced from the stage that he would not be able to do it.

People were stunned by the news as he had been in the hall all evening - he had to leave quickly once he found out he had tested positive for Covid.

There have been strict precautions in place for anyone who is due to meet the president, so Mr Martin was testing regularly.

This was due to be the big reconnecting after the pandemic, and Mr Martin was going to have his opportunity to go to the White House and take part in the ceremony.

We have been told that the taoiseach is in good spirits, and the latest indication from his team was that "not in person" options were being explored for the ceremony.

Earlier, President Biden and Mrs Pelosi addressed the gathering.

Mrs Pelosi issued a warning to the UK over the protocol.

She said that if the "border is hardened there will be no UK-US trade deal".

She also warned against any move which "imperils" the Good Friday Agreement.