US Secretary of State Condoleezza Rice has said that Nato foreign ministers have held their "best" discussion on Iraq since the fall of Saddam Hussein.
Rice is on a fence-building mission, correspondents say
Ms Rice, speaking after the meeting in Brussels, said the alliance was united and knew the work it had to do.
But she said the US still had concerns about the possible lifting of a EU arms embargo against China, and Iran's alleged nuclear weapons programme.
US Defence Secretary Donald Rumsfeld is also due to hold talks in Europe.
The secretary of state is nearing the end of an eight-day tour of Europe and the Middle East during which she has sought to soothe tensions with European nations, says BBC Europe correspondent Tim Franks in Brussels.
However, deep differences remain between the two, he says.
Speaking at a news conference with Ms Rice, Nato Secretary General Jaap de Hoop Scheffer said relations between the US and its European allies over Iraq had "turned a corner" after landmark elections there last month.
After meeting with EU officials and European Commission President Jose Manuel Barroso, Ms Rice said the US and EU had "unity of purpose and unity of message" on the issues that mattered.
RICE'S SEVEN-DAY TOUR
Fri: Met UK's Tony Blair and Foreign Secretary Jack Straw in London; talks with Germany's Gerhard Schroeder in Berlin
Sat: Talks with leaders in Germany, Poland and Turkey; met Russian foreign minister in Ankara
Sun: Met Turkish government, then on to Israel to meet Ariel Sharon
Mon: Talks with Mahmoud Abbas in West Bank
Tue: Met Italian counterpart in Rome, then on to Paris to deliver speech
Wed: Talks with French ministers, then on to meet Nato and EU officials in Brussels and Luxembourg
Thurs: Returns to Washington
But Ms Rice also said that the US and the EU were "still in open discussion" about how to deal with proposals to lift an EU arms embargo on China.
"The United States has very specific concerns," she said, citing China's human rights record and regional stability.
"We do have to worry about the military balance in the region and we have concerns about technology and its transfer," she said.
Ms Rice repeated earlier warnings that Iran "must live up to its international obligations".
In a US television interview before she travelled to Brussels, Ms Rice said European countries needed to get tougher with Tehran in negotiations to bring a halt to Iran's nuclear programme.
The UK, France and Germany have offered Iran trade concessions if it gives up its nuclear programme. Iran has agreed to temporarily suspend its uranium enrichment activities as the negotiations continue.
Iran says its nuclear programme is peaceful, but the US claims Iran is on the path to developing nuclear weapons.
Iran has signed the Nuclear Non-Proliferation Treaty (NPT), which prohibits the development of atomic weapons. The United Nations Security Council has the power to impose stringent sanctions on Iran if it is found to be in breach of the treaty.
In Nice, Mr Rumsfeld is expected to call on Nato colleagues to do more for the military effort in Iraq.
Nato said it would contribute 300 personnel for a training mission, but so far there are fewer than 100 on the ground.
The US-led invasion of Iraq during US President George Bush's first term badly strained US ties with Europe.
Some countries, notably France and Germany, said they would have nothing to do with operations in Iraq. Spain initially sent troops but then decided to pull them out after a change of government.