In serial meetings over three days, which included talks yesterday with President Bill Clinton, Mr Annan sought to begin turning the page on UN- US relations. "This is a time for healing," he said on his arrival. "I want to put behind us our differences and our sometimes acrimonious disagreements".
At the White House, Mr Annan vowed again to launch a serious programme of UN reform by the summer, while Mr Clinton laid out his own plans to settle most of the outstanding American debt to the UN of more than $1bn (pounds 600m) by 1999. It was an exchange of promises, however, that may be harder for either side to honour than anyone was willing yesterday to admit.
Mr Annan comes here with one overriding advantage: his name is not Boutros Boutros Ghali. Indeed, it was the Clinton administration that propelled him to the mountain-top by blocking Mr Boutros Ghali's re-election as Secretary General, claiming he had been too reluctant to attempt serious UN reform.
"Some have suggested that this visit will be my American honeymoon," Mr Annan quipped during the flight from New York. "Others say I am walking into the lion's den".
That there has already been a change in atmosphere, at least, is evident. At a reception hosted on Wednesday night by Vice President Al Gore, Mr Annan joked easily about the conspiracy claims circulated by the UN's shrillest critics - that it is bent on world domination. "You can tell your people that we don't have any black helicopters and we are not about to invade," he said. Mr Annan's spokesman, Fred Eckhard said: "The vibrations are very good".
Among the UN aides also on the Washington visit is Maurice Strong, a Canadian businessman appointed by Mr Annan last weekend to head-up a reform task force. Mr Strong, who is receiving $1 in salary for his efforts, is charged with coming up with a broad reform package within six months.
It remains uncertain, however, whether anything Mr Strong proposes will be strong enough medicine to impress the UN's many detractors on Capitol Hill. Among the most important of these is Jesse Helms, the sceptical chairman of the Senate Foreign Relations Committee with whom Mr Annan also had a first meeting yesterday.
Mr Strong has already warned that any reforms - which are likely to affect not just the UN Secretariat but also all of its specialised agencies and funds around the world - will have to win the support not just of the US but of all the UN membership, including countries in the developing world. "That means that not everything the US wants is going to come out they way they want it," he said in Washington.
Winning over Congress is vital, however, because without its support, President Clinton's repayment plan will turn to dust and the financial crisis that the UN has been struggling through for years will worsen. In the draft 1998 budget that will go before Congress shortly, Mr Clinton is asking that $100m in US dues be paid off in October this year while an additional $900m would be dispersed later, probably in 1999, on condition that reforms had been executed.
"We will do our part," Mr Gore told Mr Annan at Wednesday's reception. "We respect you for the person you are are and the leader you have become".