It may have been Hillary Clinton who took centre stage as she confirmed her high-profile role in the new Obama Administration. But it was another, lesser-known woman in the national security line-up who holds the key to the most fundamental policy shifts expected after Inauguration Day.

Susan Rice, Barack Obama’s chief foreign policy adviser, was named today as his Ambassador to the United Nations, the first envoy since the Clinton era to be elevated to cabinet status. Her appointment may herald the beginning of a new era for the battered relations between Washington and the UN, and for American diplomacy itself.

Ms Rice, a personal friend of the President-elect, is the first Obama “face” to be named to the Cabinet amid widespread disquiet among his supporters over the appointment of so many well-worn figures from previous administrations.

As his foreign policy adviser, she has spent the last year working with Mr Obama on plans for an ambitious but controversial diplomatic push to bring America’s adversaries in from the cold.

Mr Obama is serious about withdrawing US combat troops from Iraq, pursuing talks with Iran, Cuba and North Korea, and closing Guantanamo Bay. He also wants to expand greatly the number of foreign diplomatic posts and civilian reconstruction teams in areas threatened with Islamic extremism.

However, such moves will invite attacks begin from the Right that Mr Obama is ceding ground to America’s enemies. The President-elect’s best riposte to such criticism may come from Robert Gates, the Republican heavyweight he has convinced to stay on as Defence Secretary.

Mr Gates espouses a surprising number of Mr Obama’s beliefs, including the damage that the use of military power over diplomacy has done to America’s influence. It was he that made popular the statistic oft quoted by Mr Obama: that the United States has more military marching band members than it does foreign service officers.

Although Ms Rice is the sole Obama insider on the team, it is her big-hitting colleagues who are meant to provide Mr Obama with political cover. Nobody on the new national security team can be described as a dove — even Ms Rice, whose experiences in Rwanda following the genocide shaped her evolution into a liberal interventionist. “I swore to myself that if I ever faced such a crisis again, I would come down on the side of drastic action,” she said of her trip in 1994 as an official in the Clinton Administration — which was heavily criticized for its failure to intervene.

The new ambassador can expect a warm reception at the UN headquarters in New York. Mr Obama hopes she will be able to drum up support for UN reform in return for greater co-operation from Washington. Relations between the UN and Washington never quite recovered from the brief but tempestuous tenure of John Bolton, the abrasive ambassador whom President Bush sent to force reform on the institution. He famously said of the UN headquarters: “If you lost ten storeys today, it wouldn’t make a bit of difference.”

Mr Bolton declined to comment on Ms Rice’s appointment but condemned the decision to elevate the role to a cabinet position. “It overstates the role and importance that the UN should have on US foreign policy,” he said.

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