There will be “no chance” of a US-UK trade deal being signed off if there is a return of a hard Irish border after Brexit, US senator Chris Murphy has said.

The Connecticut Democrat, a member of the influential US senate foreign relations committee, said on a visit to Dublin on Friday that Congress would have “the final say” on any trade deal with Britain and he did not think there was the support to ratify an agreement “if there are big outstanding questions about the peace process”.

“We are all friends of Britain – it is an unbreakable bond – but we can’t compromise the sanctity of the Good Friday Agreement and folks in [the UK] parliament need to know that,” he said.

Mr Murphy is the first US senator to raise publicly the prospect of blocking a trade agreement with the UK if there is a hard Irish border after Brexit.

Senior Irish-American figures in the House of Representatives have threatened to oppose any future agreement with Britain if peace is jeopardised.

The Democratic senator told reporters after a meeting with Tánaiste Simon Coveney that his preference was for a US trade deal with the EU to be prioritised ahead of any agreement with the UK, as Taoiseach Leo Varadkar suggested during his White House meeting last week with US president Donald Trump.

“There is much more consensus in Congress about the priority of protecting the Good Friday Agreement. Not as many share my view that we should do an EU agreement before a Britain agreement but, in the United States Senate, it only takes a minority of senators to stop a trade agreement,” said Mr Murphy.

Trump criticism

He criticised the Trump administration for leaving the role of US ambassador to Ireland vacant for more than two years.

BREXIT: The Facts Read them here

Big days of meetings in Belfast and Dublin to talk about what the future of #Brexit will mean for the Irish peace process. Follow along behind the scenes on my Instagram ➡️ https://t.co/Dh82SchRhX pic.twitter.com/TcEgoQR1EW — Chris Murphy (@ChrisMurphyCT) March 22, 2019

“There is no excuse for this post remaining unfilled for this long,” he said.

The White House only last week submitted the file on Mr Trump’s nominee as ambassador, Ohio businessman Ed Crawford, to the foreign relations committee, which must approve his appointment.

“Assuming that there are no issues, I would hope that we would get him on the ground here as quickly as possible,” the senator said.

He had “an open mind” about the appointment of a US special envoy for Northern Ireland.

Mr Murphy said he wished Mr Trump “wasn’t such an unconditional cheerleader of Brexit” but sought to temper expectations that the president’s support for the UK’s exit from the EU might lead to a quick trade deal.

If we reward Britain’s departure from the EU with a quick trade agreement, it is another arrow in Russia’s quiver

“I worry that the only voice that is getting through in the Brexit debate is the president’s,” he said, arguing that Mr Trump does not control Congress and claiming he did not understand international trade.

Russian attacks

There was a “growing worry” in Congress about the long-term stability of the EU given Russia’s attacks on it, he said. He argued that the US should show a preference for multilateral institutions rather than a bilateral arrangement by agreeing a deal with the EU first ahead of the UK.

“If we reward Britain’s departure from the EU with a quick trade agreement, it is another arrow in Russia’s quiver,” he said.

The senator said he supported the EU and UK agreeing to an extension to the article 50 Brexit process to April or May, saying it was “too complicated to rush given that the consequences are permanent”.

He drew parallels between the political tensions around Brexit and the Trump administration.

“The exhaustion you feel with Brexit is the same exhaustion that we feel with the president and his daily social media barrage,” he said.

The Democrat, who has ruled himself out as a presidential contender in 2020, predicted a “wild” Democratic race and “some big fights” in the primary, but said he believed the level of enthusiasm within the party would win back the White House.

“The louder our primary is, the better, I think, it is in the end,” he said.