Relaxing by the seaside, US President George W. Bush and Russia's Vladimir Putin make a fresh bid to nurse the two superpowers' fractured relationship at the Bush family retreat Sunday.

"The President wanted to have this different kind of meeting, a more informal consultation... not with a lot of staff, in a more relaxed environment," a senior US administration official said.

Tensions peaked between the former Cold War enemies in recent weeks over US plans to plant parts of a missile defense system in Europe.

The family compound in Kennebunkport, in the northeastern state of Maine, was chosen as a place "where they can talk through the relationship, the opportunities for cooperation and the areas where there's tension," the official said.

Neither side has yet shown any desire to make a major concession ahead of the informal get-together, however. It is the second meeting in a month of the presidents, who are both due to step down next year after serving two terms.

The two leaders will not have a pre-set agenda, but discussions on the missile shield, the sharpest thorn in US-Russian relations, are likely to hog their attention.

The United States wants to install missile shield components in two former Soviet-dominated countries -- a radar in the Czech Republic and missile interceptors in Poland -- to protect its European allies from "rogue" states like Iran.

But Russia sees this hardware as a threat.

"Russia will have to secure its interests," Kremlin spokesman Dmitry Peskov said ahead of the meeting. "There is flexbility in our approach but not an endless flexibility."

"We don't see any threat coming from Iran for the United States and Europe in the foreseeable future," he said.

Putin surprised Bush at their meeting earlier this month by suggesting an alternative to installations in central Europe: an existing radar station in Azerbaijan. But the White House is circumspect about the idea.

"The question is, what does the (Azerbaijan) radar do, what are its capabilities, and what is the role it could play?" the top official said.

"These systems take a long time to build, so it's not as if there isn't time to have a thorough conversation."

Experts say neither side appears ready to compromise on certain other issues, such as the southern Serbian province of Kosovo. Washington backs its Albanian majority's push for independence, while Russia sides with the Serbs.

"There really are no obvious candidates for a breakthrough issue that would impart a positive momentum to the broader relationship," said Steven Pifer, of the Center for Strategic and International Studies, a Washington-based think tank.

Presidential elections in 2008 in both countries also complicate relations.

"This is about the two men having a quiet, more informal conversation about these issues, surely, but also sort of where we're heading in the relationship as we go into the last 18 months of our president," the US official said.

It will also cover "how we're going to handle the issue of US-Russian relations in this unique period in their political calendar and... in ours."

Putin is constitutionally obliged to stand down after the March presidential election. But he is widely expected to retain a powerful role in Russia.

White House spokesman Tony Snow said no "grand initiative" or "bold announcement" was expected from Sunday's talks but they will cover some hot diplomatic topics.

These include North Korea and Iran -- whom the world community is pressing over nuclear arms-related issues -- and the conflict-stricken Middle East, Snow said.

Putin will become the first foreign leader ever to be hosted by Bush in Kennebunkport.

The family property sits on a rocky outcrop overlooking the ocean in a region known for its lobster, where the 43rd US president likes to fish, following the example of his father George Bush, the 41st.

Leisure time is scheduled for between Sunday and Monday, when Bush senior may join them.