A senior US senator sharply criticised Haiti's president, portraying him as an ineffectual leader who was hindering recovery from January's devastating earthquake.
Richard Lugar, the senior Republican on the Senate Foreign Relations Committee, advised US legislators to reconsider sending money to Haiti if reforms were not made.
The paper is another slap in what has become a protracted fight between the Senate committee and Haitian president Rene Preval.
After earlier critical reports from the panel, including one issued by its chairman, Democratic senator John Kerry, Mr Preval called a news conference last month to reject proposals aimed at stamping out alleged corruption ahead of the November 28 presidential election.
He accused the committee of overreach and called the proposals "inadmissible".
The 16-page paper issued yesterday says Mr Preval has "demonstrated marginal capacity to lead his country's reconstruction". A section on the last two decades of US aid and investment in Haiti is titled 'Observations: A lot of money but few results'.
"President Preval's actions do not suggest a departure from the self-destructive political behaviour that has kept Haiti the poorest country in the Western Hemisphere," Mr Lugar wrote in an opening letter.
In an accompanying statement, he warned: "It is incumbent upon Congress to reassess our government's investments in Haiti if this partnership is in question."
The Senate is considering a bill that includes $1.15bn (€892.75m) in US aid pledged for Haiti's reconstruction at a March donors conference. Less than 10% of the total €4.15bn in international donations pledged for the first two years of rebuilding has been delivered.
Committee staff declined to comment further on what measures it would take if Mr Preval again rejected their advice.
The report's proposals cut to the heart of some of Haiti's most intractable pre-earthquake conflicts, which it said had left rebuilding "almost at a standstill because of a dearth of political will and leadership".
It calls for modernisation of the land-title system, a mechanism that plunges anyone trying to build on undeveloped terrain into a morass of competing claims, contradictory deeds and inter-family conflicts.
Aid group Oxfam studied land-title reform for six months after the quake before deciding the problem was too thorny to be tackled in the short term.
The Senate report also advises Haiti's leaders to make it easier to start and operate businesses and urges them to set up a six-month term to evaluate investment proposals. In the past, it said, "some dragged on for years until investors simply gave up".
The report was prepared after meetings with 10 of Haiti's most powerful businessmen, more than a dozen of their counterparts in the neighbouring Dominican Republic, US diplomats and World Bank staff.
The lone Haitian government official listed is Lionel Delatour, who consults for the Haitian committee aimed at increasing garment exports to the US.
Dominican entrepreneurs are quoted as complaining that corruption, crime, kidnapping, political instability and poor infrastructure threaten to make their involvement in reconstruction "a waste of time".
Mr Preval has been president for nearly 10 of the last 15 years. In that time Haiti has suffered government upheaval including the bloody ousting of ex-president Jean-Bertrand Aristide, the tumultuous reign of a US-backed interim government, numerous hurricanes and floods and the January 12 earthquake.
His term is scheduled to end in February, with a successor to be chosen in the November election.