"We will make clear that we will lift our objections to an Iranian application to the WTO and that we are prepared to lift an objection to the licensing of spare parts for Iranian commercial aircraft," Rice said on Friday.
"The decision that the president has taken is that the United States will make an effort to actively support the EU3 negotiations with the Iranians," Rice added, referring to a British-French-German diplomatic effort to negotiate an end to Iran's suspected nuclear weapons programme.
The united approach marks a milestone in efforts to curb what Washington believes are Iran's attempts to develop nuclear arms. Iran has denied it is seeking atomic weapons and has said its civilian nuclear programme is for peaceful power generation.
The US decision to embrace economic incentives is a significant reversal from Washington's previous refusal to reward Iran for what it regards as bad behaviour.
Britain, France and Germany, in turn, shifted gears on Friday and told their European Union partners they would support referring Iran to the UN Security Council if it resumes uranium enrichment or breaches nuclear commitments.
The three countries initially had been reluctant to commit to bringing the issue to the Security Council, which could impose sanctions.
"We share the desire of European governments to secure Iran's adherence to its obligations through peace and diplomatic means"
US Secretary of State
Rice was vague on whether the United States would actively pursue sanctions at the Security Council, saying it was too early to make such decisions.
Rice said the administration will consider allowing the aircraft spare parts sales on a case-by-case basis. Many of the sales would be from European Union countries.
"We share the desire of European governments to secure Iran's adherence to its obligations through peace and diplomatic means," the secretary said.
"The Europeans have a strategy which is to show the Iranians that if they are prepared to live up to their international obligations there is an alternative path to confrontation and there is a path to a better future," Rice said.
"We are supporting that diplomacy but this is most assuredly giving the Europeans a stronger hand, not rewarding the Iranians," she added.