LONDON, Dec. 2 (Xinhua) -- Leaders of major Western states start to arrive Monday night in London for what has been described as one of the most important NATO summits in its 70th birthday year.

NATO is at a crossroads, say some observers, while Britain is just over a week away from a general election that will determine its fate within the European Union.

French President Emmanuel Macron's recent comment that NATO is "brain dead", coupled with U.S. President Donald Trump describing the alliance as obsolete, is not the kind of birthday wishes NATO's Secretary General Jens Stoltenberg wanted to hear.

Leaders are expected to arrive in London to prepare for a NATO birthday bash being thrown at Buckingham Palace Tuesday by Queen Elizabeth for the leaders of NATO member states.

British Prime Minister Boris Johnson will take a break from electioneering ahead of the Dec. 12 vote, with opinion polls suggesting main opposition Labour is closing the gap.

Security around London has been stepped up in the wake of the deadly terror attack near London Bridge last week.

The NATO summit takes place Wednesday at a hotel in Watford, north of London where a ring of steel and high security will be in place to guard the attendees.

Leading academic Professor John Keiger said this week will be seminal for both Johnson and Macron.

Writing in the Spectator journal, Keiger, a former research director in the Department of Politics and International Studies at the University of Cambridge, said Johnson is hosting one of the most important NATO summits for years.

"Its significance is not because it marks the Alliance's 70th anniversary, but because of President Macron's 'disruptive' and trenchant criticism of the Atlantic Alliance as close to 'brain dead', which has touched a nerve," Keiger said.

German news magazine Der Spiegel has put the NATO summit under the microscope, saying political disputes overshadow the alliance's 70th anniversary.

"In recent years, NATO has been militarily successful, but it has also been a political problem child. Indeed, Emmanuel Macron has disparaged it as 'brain dead' and Donald Trump once called it obsolete. The alliance is clearly at a crossroads," Der Spiegel said in an online article.

Stoltenberg acknowledged there are disagreements among the allies, on things like trade, climate change and the approach to Iran and northern Syria.