By Jonathan Beale
BBC state department correspondent
Condoleezza Rice is in London with a lot on her plate.
Consolidating democracy in Afghanistan is top of the agenda
The purpose of the US Secretary of State's latest round of diplomacy is an international conference on Afghanistan.
But there are other pressing issues. How does the international community respond to the Palestinian Islamic group Hamas' shock election victory? And what can it do to halt Iran's nuclear ambitions?
Afghanistan may appear to be the least pressing problem but it is of critical importance to US foreign policy. President Bush wants Afghanistan to become a beacon of democracy to the wider world.
America has already pumped $10bn (£5.6bn) into rebuilding the country in the five years since the end of the war.
On Monday, Condoleezza Rice is expected to announce "a major financial contribution" for the coming year. There will also be international help on debt relief.
But unlike the previous donors conference in Bonn - this one will aim to show that Afghans are now able to govern themselves.
The Afghan government is committing itself to specific goals on security, governance and economic affairs.
The conference coincides with a major shift in Nato troops operations in the country.
Britain and other nations are moving troops to the south so that US forces can be sent to the east to tackle the remnants of the Taleban.
But the presence of more troops and the drugs trade illustrates that Afghanistan is still some way off from becoming that shining example of US nation building.
Dealing with Hamas
On Monday afternoon there will be a meeting of the Middle East "Quartet" of mediators - the US, EU, UN and Russia.
Their task is to work out a strategy - if one can be worked out - of how to deal with Hamas.
Ms Rice has already set out America's conditions for dealing with Hamas - proscribed by the US as a terrorist group .
It must renounce violence, lay down its arms and recognise Israel's right to exist.
The US and the EU have been the biggest donors of aid to the Palestinians - around a $1bn every year. But the US has made clear that it will not give any financial support to a Hamas government.
However, the Quartet cannot afford to desert the Palestinians if there is to be any chance of resuming peace negotiations.
Nor can they allow a country like Iran to fill the void if they pull the financial plug. Money could still be channelled through various non-governmental groups and perhaps Palestinian leader Mahmoud Abbas.
But the Bush administration and politicians on Capitol Hill will want guarantees that aid will not end up in the hands of terrorists.
That would undermine President Bush's "War on Terror".
Pressure on Tehran
The challenge posed by Iran's nuclear programme is just as difficult.
Ms Rice says the Iranians are "feeling the heat" of international concern and she is determined to keep up the pressure.
The US - supported by the EU - wants to refer Iran to the UN Security Council.
They hope the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), will take that step when it meets in Vienna on Thursday.
But both China and Russia - who both hold the veto - have made known their reluctance. It is not even clear what should be done if Iran is referred. Talk of sanctions still seems a long way off.
The US insists it has the votes to have Iran hauled before the Security Council but admits that there is still a lot of work to be done on tactics.
Ms Rice has just completed her first year as Secretary of State. But this week could prove her most difficult yet.