Obama arrives to address crowds in Berlin

US president Barack Obama has arrived in Berlin for a visit at the end of which he will address crowds at Brandenburg Gate.

US officials say he will propose cuts of one-third in US and Russian nuclear arsenals and will also seek cuts in the number of warheads in Europe.

In 2008, as a presidential candidate, he drew a crowd of 200,000 in Berlin.

The visit comes after G8 leaders backed calls for holding Syrian peace talks in Geneva "as soon as possible".

This is Mr Obama's first visit to Berlin as American president. His address to students and government officials at the Brandenburg Gate comes almost 50 years after John F Kennedy's celebrated "Ich bin ein Berliner" speech.

He is first due to have talks with Germany's chancellor, Angela Merkel.

In his speech at the Brandenburg Gate, Mr Obama is expected to make what US officials describe as "a call to action", for the West to engage in major global issues.

He is also likely to speak in detail about ways of promoting democracy and ending conflicts as well as tackling climate change and nuclear proliferation.

US officials say he will seek cuts in US and Russian nuclear arsenals of one-third from the levels agreed in the New Start treaty in 2010.

He will also urge reductions in the number of tactical nuclear warheads deployed in Europe, the officials say.

Chancellor Merkel, who faces the voters in September, has already made it clear that she will seek "more transparency" about US internet and telephone surveillance programmes exposed last week.

"We have to be clear, what is being used, what is not being used," she said, adding that while secret services had to fight terrorism, "it must be proportional".

The head of America's electronic spying agency, Gen Keith Alexander, said on Tuesday that the programmes had helped thwart 50 attacks since 2001.

When Mr Obama was last in Berlin in 2008, he spoke to ecstatic thousands of America's "mistakes" and how the Afghan people needed "support to defeat the Taliban".

He may now take the opportunity to explain why he has ordered peace talks with the enemy America has fought for 10 years, says the BBC's North American editor Mark Mardell.

After the G8 meeting in Northern Ireland, President Obama described the planned Taliban talks as "a very early step" towards reconciliation in Afghanistan.

Mr Obama did not comment on the summit's communique on Syria. But Deputy National Security Adviser Ben Rhodes acknowledged that there were "difficulties ahead" in resolving the issue.

But speaking to reporters on the flight to Germany, Mr Rhodes added: "Given the various ways the G8 could have gone, we believe that on the key issues of political transition, humanitarian support and chemical weapons investigation, it's very helpful to have this type of signal sent by these eight countries".

UK Prime Minister David Cameron, who hosted the summit in Enniskillen, Northern Ireland, said the G8 managed "to overcome fundamental differences" on the raging Syrian conflict.

However, no timetable for the Geneva talks was given, and the G8 communique did not mention what role Syrian President Bashar al-Assad could play in the future.

This remains a key stumbling block, with Russia backing President Assad, while the US and its European allies are supporting the rebels.

The communique is largely a reaffirmation of what was said at the Geneva Conference in June 2012, reports the BBC's Jonathan Marcus at the summit in Enniskillen.