Foreign Secretary David Miliband is meeting Hillary Clinton in Washington for the first face-to-face talks between a British minister and the new US administration.
Issues high on the agenda are expected to be Afghanistan, where both the UK and the US have large numbers of troops, Pakistan, Iran and the Middle East.
The Foreign Secretary has spoken several times via the telephone to Mrs Clinton, the new US Secretary of State, since President Barack Obama's inauguration last month.
But Mr Miliband will be the Obama administration's first high-level British visitor and will be able to talk through the details of America's new foreign policy.
There are growing expectations that Mr Obama may call on Britain to deploy more troops to Afghanistan as the US seeks to make more decisive gains against the Taliban.
Mr Obama has also indicated his desire to improve US relations with Iran, including the possibility of talks, after years of diplomatic stalemate over the latter's nuclear ambitions.
Mr Miliband and Mrs Clinton are also likely to talk about the situation in Gaza following Israel's bombardment of the enclave, as well as the wider Middle East peace process.
After meeting with Mr Miliband, Mrs Clinton is due to hold talks with her German counterpart, foreign minister Frank-Walter Steinmeier.
Officials from the US State Department said Iran and Afghanistan would be at the top of the agenda of both meetings.
On Wednesday the five permanent members of the UN Security Council are to meet in Germany to discuss Tehran's nuclear ambitions.
