Barack Obama will Wednesday propose major cuts in US and Russian nuclear stocks, making a pitch for his own place in history in an evocative open-air speech during his first visit as president to Berlin.

Almost 50 years to the day since John F. Kennedy declared "Ich bin ein Berliner" and 26 years since Ronald Reagan exhorted "Tear down this wall!" Obama will unveil plans for a one-third reduction in Cold War nuclear arsenals.

He also met German Chancellor Angela Merkel, with whom he usually has respectful relations, but who is pointedly demanding details on the exact extent of US spy agency surveillance programmes.

The US president was set to use his speech at Brandenburg Gate to propose cutting US and Russian strategic nuclear warheads to around 1,000 each, and also seek cuts in tactical nuclear arms stocks in Europe.

"We will seek to negotiate these reductions with Russia to continue to move beyond Cold War nuclear postures," a senior US official said.

It remains unclear whether Russian President Vladimir Putin, with whom Obama had a frosty meeting at the G8 summit in Northern Ireland on Monday, will agree to such substantial weapons cuts.

Russia has previously demanded changes to the US missile defence system before agreeing to return to the nuclear agenda.

Obama will also commit to attending a nuclear security summit in The Hague next year, and to hosting his own version in 2016 in the last year of his presidency.

Obama inaugurated the first such summit, designed to ensure unsecured nuclear stocks do not fall into the hands of terrorists, in Washington in 2010 and went to a follow-up meeting in Seoul two years later.

Wednesday's announcement is intended to ensure that his nuclear counter-proliferation agenda remains at the centre of his foreign policy legacy, following the conclusion of a Strategic Nuclear Arms Reduction Treaty with Russia during his first term.

The US has around 20 nuclear warheads still stationed in Germany, down from about 200 when the Berlin Wall fell in 1989.

Obama remains popular in Germany -- a poll this week for Die Zeit newspaper showed that 60 percent of Germans were satisfied with his leadership.

And 42 percent said he was more successful than Merkel, Germany's most popular post-war leader who is standing for a third term in September elections, versus 34 percent who thought the chancellor had achieved more.