The sides have differing views on Hamas
US President George W Bush has urged European leaders to take "swift and decisive action" against the Palestinian militant group Hamas by cutting off its funding.
Speaking at a joint summit between US and European leaders, Mr Bush said the dismantling of such groups would be the "true test" of the so-called roadmap for peace in the Middle East.
The two sides also made a joint call to Iran and North Korea to abandon any ambitions they may have of possessing nuclear weapons.
The two countries have been described by Mr Bush in the past as part of an "axis of evil", along with Iraq.
Mr Bush said the US and Europe were "working closely to meet the proliferation challenges posed by North Korea and Iran."
His meeting with senior EU figures was the first since transatlantic relations were strained by the war on Iraq, and their joint statement is being seen as an attempt to present a united front.
However, correspondents say continuing differences became apparent as Mr Bush pressed the EU to crack down on Hamas.
"Progress toward this goal will only be possible if all sides do all in their power to defeat the determined enemies of peace, such as Hamas and other terrorist groups, he said.
The EU for its part insists that Hamas has political functions as well as a militant wing.
Brussels and Washington are trying to demonstrate at the summit that they have entered a post-war era of closer co-operation following sharp divisions over the conflict in Iraq.
An extradition deal between the two sides was signed on Wednesday, authorising the sharing of information and broadening the scope of crimes to which extradition would apply.
EU-US extradition deal
Joint declaration on WMDs
Agreement on accessing bank accounts
Talks on inspecting shipping containers
Talks on whether Hamas should be banned in EU
Discussing way forward on GM foods
Discussing open skies policy
The deal follows an EU pledge struck in the wake of the 11 September attacks to help the US combat terror attacks.
Both sides also agreed to hold talks this autumn on an open-skies agreement liberalising air travel between the EU and the US, replacing existing bilateral agreements with individual European countries.
EU and US leaders played down divisions, with president of the European Commission Romano Prodi saying that unity was essential for dealing with the world's problems.
"When Europe and United States are united no problem and no enemy can stand against us," he said.
However BBC correspondent Rob Watson in Washington said that despite such soothing words the different approach to Hamas shows that new talk of unity still has its limits.
Disagreements remain over several issues, such as genetically-modified crops, which the US is much more keen than the EU to develop and exploit.
Ties between the US and EU have been under strain
The US president has criticised EU GM policies, saying they contributed to famine in Africa, while Europe has hit back, insisting that Brussels did much more than Washington to feed the hungry.
Separate divisions also exist on the International Criminal Court, established in The Hague in the face of the US refusal for its soldiers to be subject to the court's jurisdiction.
"The United States and Europe, together, have an obligation to look beyond themselves to the world," said a senior official in the Bush administration.
"That is where the threats to freedom are, the threats to security could come from, and where the opportunities are for joint action."
The deal was agreed after the EU, which is opposed to capital punishment, won the right to refuse extradition in cases where the maximum penalty was death.
A separate agreement allows law enforcement agencies on both sides of the Atlantic to access bank accounts in some criminal and anti-terror inquiries.
And discussions will be held on allowing US officials based in European ports to inspect shipping containers due to set sail for the US.