President Donald Trump's administration and presidential candidate Joe Biden have joined those paying tribute to John Hume.
US Secretary of State Mike Pompeo said the former SDLP leader displayed "integrity and courage" and played a "profoundly important role" in the north's transition from violence to peace.
"Throughout his career, John Hume believed that just and lasting political solutions could only be achieved through peaceful means, and as a central architect of the Belfast/Good Friday Agreement he worked tirelessly to make these aspirations a reality," he said.
"Mr Hume's influence extended far beyond the shores where he lived."
Mr Pompeo added: "During the darkest days of Northern Ireland's recent past, he won the friendship and respect of countless Americans.
"His early and sustained influence in bringing US political and economic support to Northern Ireland cannot be overstated, and this profound partnership and friendship continues today.
"Many Americans who care deeply about Northern Ireland will mourn the passing of Mr Hume, and the extensive contribution that he made to build peace and to strengthen our transatlantic relations. Our thoughts are with his wife, Pat Hume, and his family at this difficult time."
Former vice president Mr Biden said the world has lost a "great man of peace".
"John Hume committed his life to the principles of non-violence, and, through his faith, statesmanship, and perseverance, he helped bring Northern Ireland through the Troubles to a better tomorrow," he said.
"He saw the power of political leadership to bring a divided people together around a common purpose, without which the Good Friday Agreement would never have come to pass.
"Jill and I send our condolences to the entire Hume family. May his leadership and the example of his life continue to inspire future generations of peacemakers and patriots to create a world more grounded in civil rights, tolerance, equality, and democratic freedoms."