A bilateral trade deal between the US and the UK is “desirable” but will not progress while the Northern Ireland peace deal is being used for domestic political purposes, one of the most powerful American congressmen has warned.

Richard Neal, the chairman of the ways and means committee, has told the Guardian: “We will not entertain a trade agreement if there is any jeopardy to the Good Friday agreement.

“A bilateral trade agreement with the UK is desirable – there’s no question about that. I’m very open to that. But what I’m not open to is holding the Good Friday agreement hostage over domestic politics.”

Neal, who has taken a keen interest in Northern Ireland over the past three decades, is a key figure in US trade deals and negotiated the US-Mexico-Canada Agreement.

His committee writes trade bills and without its support a deal will not be approved.

In an exclusive interview from Washington, he denounced those who say the Brexit deal has killed the Good Friday agreement on the grounds that unionists did not consent to the arrangements negotiated with the EU.

“We are concerned that the protocol is being used to hold the Good Friday agreement hostage,” he said.

“The argument being applied by some is reckless and demagogic.”

Neal’s comments come a day after the US trade minister Katherine Tai dashed hopes of any imminent post-Brexit free-trade deal, saying an agreement was not worth spending “years and a lot of blood, sweat and tears” over.

Neal said he had personal reassurances from both the Northern Ireland secretary Brandon Lewis last week and Boris Johnson on a recent trip to Washington that there was no desire to jeopardise the Good Friday agreement.

While he went “back and forth” with Lewis, Neal said he had a “good meeting” and they both agreed it was “not healthy for political parties to suspend government when they disagree on legislative detail”, a reference to a recent decision by the DUP to pull the first minister out of the Stormont executive.

Neal confirmed that he has considered leading an American delegation to Dublin and London to reinforce his message about the peace deal and stability in Northern Ireland.

He said the peace deal was precious, hard-won and should be celebrated as a template for negotiations around the world with significant compromises on both sides paving the way for long-term peace.

“Two generations of children have grown up in a different atmosphere than what the north looked like 30 years ago.

“I think we need to remind everybody of the risks and the chances that were taken by all parties to get to the Good Friday agreement. We should be celebrating it as a template for the world order.”

He pointed out that in the referendum south of the border the Republic of Ireland agreed to change articles two and three of the constitution, which laid claim to the six counties in Northern Ireland, while the UK relinquished the hard border.

“The last thing we want to do is jeopardise that spectacular agreement,” he said.

The dispute over Northern Ireland was “one of the longest in the history of the western world” said Neal, and “we came up with an agreement”.

“That agreement has withstood 24 years and it has received great scrutiny.”

He added he had heard no argument so far that suggested “there would be a quid pro quo of the protocol for changes in the Good Friday agreement”.