John Kerry has met with the UK’s prime minister, David Cameron, in London, as part of his first trip abroad as US secretary of state.
It is the first stop on his tour, which will take in Europe’s main capitals, Turkey and the Middle East.
Syria will be high on the agenda, and Mr Kerry is also expected to talk about next month’s referendum on whether the Falklands should stay British.
The US has said it is up to Britain and Argentina to work out a resolution.
Mr Kerry, who succeeded Hillary Clinton as the top US diplomat earlier this month, arrived in London on Sunday night.
He is now meeting with British foreign secretary William Hague, having already held talks with Mr Cameron.
Falklands dispute
Mr Kerry is expected to be asked about the US administration’s views on Britain’s dispute with Argentina over the sovereignty of the Falkland Islands.
A senior State Department official told the BBC there is currently no change in the US position – the US recognises the UK’s control of the islands but takes no position on sovereignty.
BBC world affairs correspondent Naomi Grimley says the Foreign Office is flattered Mr Kerry’s first destination is London, especially as President Barack Obama seemed more attentive to Asia than to Europe in his first term.
In all, Mr Kerry will visit nine countries, including France, Turkey and Egypt on his first tour abroad.
In Berlin he will meet Syrian opposition members and representatives of nations supporting them.
Mr Kerry has said he plans to use the trip to propose ideas on persuading Syria’s President Bashar al-Assad to step aside.
His schedule will see him meet foreign ministers and leaders in European capitals including Paris, Rome and Ankara before a tour of Middle Eastern cities including Cairo, Abu Dhabi and Riyadh.
Though the Middle East peace process will be on the agenda when he visits Turkey, Egypt and Saudi Arabia, Mr Kerry will not visit Israel or the Palestinian Territories.
However, our correspondent says Mr Hague is hopeful his visit will herald a new enthusiasm for the peace process.
She says: “Mr Hague would like to see a renewed effort from the US to engage the different parties around the negotiating table.”
Mr Kerry, former Massachusetts senator and 2004 Democratic presidential candidate, has spent almost three decades in the US Senate as a member of the Foreign Relations Committee.
His visit comes as Palestinians demonstrate in the West Bank following the death in an Israeli jail of a 30-year-old man.
Palestinians say Arafat Jaradat, 30, died from torture, while Israel says a post-mortem was inconclusive and that investigations into his death continue.