Five urgent tasks for Britain's new prime minister

Britain's next prime minister will face an overflowing inbox when he takes office on July 24: delivering Brexit, building a relationship with Donald Trump, deciding what to do about Iran and governing without a majority in parliament.

The winner of the Conservative party leadership contest will be announced on Tuesday and should take office as prime minister on Wednesday.

Boris Johnson, leader of the 2016 campaign to leave the European Union, is the front-runner to succeed Theresa May. His rival is Foreign Secretary Jeremy Hunt, who voted "remain" in the Brexit referendum but has repeatedly promised to take Britain out of the EU.

Below are the most urgent tasks the winner will have to tackle:

1) Governing

To deliver Brexit, one of the most divisive policies in decades, the new premier will have to show he can win votes in parliament and govern after three years of political crisis.

But he could face a vote of no confidence in the 650-seat parliament as early as his second day in office if the main opposition Labour Party calls one.

On its own, the ruling Conservative Party does not have the majority needed for the new prime minister to survive such a vote, relying under May on the support of 10 allied Democratic Unionist Party (DUP) lawmakers to govern.

Even if the DUP backed the new prime minister in a confidence vote, a handful of Conservative lawmakers have threatened to vote against their party if Britain looks set for a no-deal Brexit.

Failure to clear this first hurdle would collapse the government and could trigger a general election.

2) Brexit

Both Hunt and Johnson want to renegotiate a new deal with the EU, ditching parts of the accord May struck with Brussels last year, which was rejected by parliament three times.

The EU has repeatedly said it will not renegotiate the legally binding part of that deal, the 'Withdrawal Agreement' which sets out a transition period to smooth Britain's exit.

The problem for the next prime minister is that the withdrawal agreement contains the most contentious part of the exit deal an insurance policy to prevent border controls between EU member Ireland and British province Northern Ireland.

EU negotiators are ready to explore several options with the new prime minister, but these fall well short of what Johnson and Hunt say they want.

Hunt and Johnson want to ditch the so-called backstop; the EU says it has to stay.

If Britain cannot negotiate a new deal, or parliament rejects whatever the new leader brings back from Brussels, the country will be headed for an unmanaged exit from the EU a so-called no-deal Brexit on Oct. 31.

Johnson and Hunt both say they have to make sure Britain is fully prepared for such an outcome because it is an important negotiating tool and they cannot rule out that it may happen.

Britain had conducted substantial work toward preparing for no-deal ahead of the original Brexit deadline of March 29, but as the date approached many expressed concern that those preparations were incomplete and had stagnated.

3) Trump and the United States

The new prime minister will need a good relationship with the United States, Britain's closest military ally and a major export market, to help mitigate any impact of stepping away from the EU its biggest trading partner.

But relations between Britain and the United States have suffered in recent weeks after the leak of confidential memos from the British ambassador to Washington which reportedly described Donald Trump's administration as inept.

How the new leader moves on from the spat which saw Trump respond angrily and the ambassador resigns could set the tone for transatlantic ties during a critical period for Britain.

Both sides say they want to agree on a swift and comprehensive free trade agreement after Britain leaves the EU, but political will is likely to determine how quickly that can be done.

4) Iran and China

The United States and European allies are pulling in different directions over the best approach to Iran's nuclear programme, leaving Britain with a difficult choice about who to align with.

Iranian Revolutionary Guards seized the British-flagged tanker Stena Impero in the Strait of Hormuz on Friday, in apparent retaliation for the British capture of an Iranian tanker two weeks earlier.

Allies are watching closely to see whether the new British leader will move towards the United States and away from the EU over Iran policy.

The new prime minister will also have to decide what role Chinese technology firm Huawei will be given in British communications infrastructure, with Trump warning that the security risks are high and could endanger intelligence ties.

That decision could also set the course of relations with China, one of Britain's top targets when it comes to building stronger trading ties outside the EU.

5) Beyond Brexit

While the next prime minister's first test will be to deliver Brexit, he will have to craft a viable long-term vision of post-Brexit Britain that can win over voters, investors and international allies.

Ultimately, the new leader will have to decide what sort of economy the United Kingdom wants and how it will pitch that to the world while choosing between aligning with either European or American regulations.