Mr Ryan, a senior member of Donald Trump's Republican party, told a central London audience this evening that US lawmakers are committed to working with the president towards a bilateral agreement with the UK.
His clear signal provides a significant boost for Theresa May as European Union leaders take the first steps towards agreeing a negotiating position for forthcoming Brexit talks.
Paul Ryan made the announcement as he visited Philip Hammond
In a speech for the Policy Exchange think-tank, Mr Ryan said: "Now that Article 50 has been invoked, the UK and the EU will determine the best path forward over the course of these negotiations.
"We want the parties to come together and strike a lasting agreement, a strong UK-EU relationship is in all of our best interests.
"In that same vein, the United States will work closely with our EU friends and chart a path forward on TTIP (Transatlantic Trade and Investment Partnership) negotiations.
"At the same time we are committed to working with President Trump and your Government to achieve a bilateral trade agreement between the United States and Britain.
"This is one of the bipartisan messages I bring with me, I bring Democrats and Republicans here to this room to this country today, to say that the United States stands ready to forge a new trade agreement with Great Britain as soon as possible so that we may further tap into the great potential between our two people."
Mr Ryan said the US could agree a trade deal soon
Ryan and Hammond met outside 11 Downing Street today
Only two months ago Ted Poe, the chairman of the congressional foreign affairs committee heralded the "special relationship" between the two nations, calling a bilateral trade deal an opportunity to "deepen our alliance even further".
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And he claimed the deal could be forged in as little as two years – as the UK fights it out with the European Union following the triggering of Article 50.
But now it seems President Donald Trump could push for a deal even sooner following Mr Ryan's announcement, made as he visited the British chancellor Philip Hammond in Downing Street today.
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Answering questions from an audience including International Trade Secretary Liam Fox and other Cabinet ministers, Mr Ryan said he cannot imagine Britain being unable to agree a trade deal with the EU even after Brexit negotiations have concluded.
He added: "This is your country, you make those decision.
"But I assume you will get an agreement, I can't imagine you won't, and I just want you to know that as your special ally, as your greatest partner, we're going to stand with you through all of this.
"We think it's in everyone's interests to have a strong relationship between Britain and the EU, we want to, as soon as the UK is ready and able, to do a trade agreement, a bilateral trade agreement."
Mr Ryan's comments come as the Prime Minister prepares to hold talks on the EU exit
Mr Ryan added: "I think what we're going through if we handle this correctly will be to bring more prosperity and security to our respective countries."
The comments come as the Prime Minister prepares to hold talks on Thursday with Antonio Tajani, the president of the European Parliament, which will ultimately have to approve any post-Brexit deal between the UK and EU.
And the news comes just a day after British Prime Minister Theresa May revealed the UK would be going to the polls again after she announced a snap general election to be held on June 8.