President Bush (search) and British Prime Minister Tony Blair (search) worked very closely together during the American president's first term, and that's likely to continue over the next four years.

Even though the English prime minister is the leader of the British Labour Party, which is similar to the American Democratic Party, Blair is not only a loyal ally, experts say he's also a link between the United States and Europe.

"He's an important voice in the EU, NATO ECM to help bring the common agenda of the U.S./British interests have in terms of security to the table and make sure those agendas get worked," said James Carafano, senior defense and homeland security expert from The Heritage Foundation.

But British analysts say Blair's relationship with Bush may become increasingly difficult because it rankles the Labour Party and its supporters. Plus, Blair soon will be up for reelection, likely next spring.

"It must be reassuring for him to see that Bush, like John Howard in Australia, has managed to win an election in spite of involvement in the Iraq war, so that must have put a smile on his face this morning," said Richard Gowan, researcher at The Foreign Policy Center, a London-based think tank. "However, it is bad news for the prime minister as far as his relations with the Labour Party."

One issue that British experts say could test the Bush/Blair alliance is Iran. The United States wants to take a harder line through the United Nations to prevent Tehran from developing nuclear weapons. Britain and Europe, however, want to continue negotiations.

"So the next few months are absolutely crucial for Tony Blair," said Victor Bulmer-Thomas, director of the Royal Institute of International Affairs in London. "He has to ensure that the policy of engagement through Europe with Iran is actually delivering. If it's not, then he will face an excruciating choice between whether to stay with his European partners, France and Germany in particular, or whether to side with the U.S."

Bulmar-Thomas says, if faced with that choice, Blair likely would side with Europe.

Click in the box near the top of this story to watch a report by FOX News' Molly Henneberg.