The Lowdown: Get your feet under the desk, then take on the US and ease Third World misery

He moves to the edge of his seat and leans forward, his gaze fixed. Mike O'Brien is in deadly serious mode. The silver-haired trade minister, who was promoted to the post just over three weeks ago, is rehearsing what could prove an extremely difficult meeting.

Tomorrow he is due to meet his US counterpart, Robert Zoellick, in his Washington office overlooking the White House. Sitting opposite the US trade representative - flanked by an American flag on one side and a collection of 19th-century prints on the other - O'Brien will say that the US needs to pull up its socks.

With seven weeks to go before the start of the next round of world trade negotiations in Cancun, Mexico, he believes the US must do more for developing countries and free trade by reducing subsidies and tariffs.

Coming fresh from the agreed European reforms of the Common Agricultural Policy (CAP), O'Brien feels that Britain and the EU now have some leverage on trade over the US. "We will say to the Americans: 'Look, the ball is in your court. We have shown that we are prepared to move ... where are you?'," he says, in his first interview as trade minister. "Obviously it is going to be difficult for them because they are in the run-up to a presidential election and the farm states are important. But they can no longer use the excuse they have been using up to now, which is: 'We don't need to move because the Europeans aren't moving.' Well, in answer to them: 'The Europeans have moved.' "

The meeting with Zoellick could be crucial in ensuring that Cancun is a success. The interests of developing counties will be central to this gathering of World Trade Organisation members. Tariffs, subsidies, bilateral agreements and protectionism in Europe and America have crippled trade in countries such as Mozambique, Zambia and Malawi, where poverty is rife.

"The key thing is that this is a developing countries' agenda," says O'Brien, and near the top of this agenda when he meets Zoellick will be medicines. During the Doha round of trade talks launched 18 months ago, America vetoed plans that would have forced its drug companies to loosen their grip on patent rights. This would have allowed cheap copycat treatments to be sold in developing countries to help tackle asthma, cancer, HIV/Aids and diabetes.

Critics argue it is no coincidence that the US failed to reach agreement on Trade-Related Property Rights (TRIPs) when the pharmaceutical lobby provided almost $60m (£37m) to the Republicans in the recent mid-term elections.

The House of Commons' International Development Committee will tomorrow warn that US opposition on TRIPs will undermine the whole Cancun development agenda. With over 100,000 protesters expected to arrive in Cancun, any sign of a poor deal for developing countries could lead to a repeat of the trouble seen at the Seattle trade talks.

O'Brien says: "If they can move on TRIPs before we get to Cancun then that will send a very good signal that the Americans are serious about the whole Doha development agenda. Don't forget we are talking about whether we can help people who are dying, leading appalling lives of suffering - who could be assisted if Pfizer and other American corporations would agree that other countries could develop drugs that cure and help those who are suffering. This is not just about trade and economic issues."

Before he was promoted to trade minister, O'Brien was the Foreign Office minister responsible for the Middle East and was regularly wheeled out to defend the invasion of Iraq. Despite his background, many groups lobbying for a better deal for developing countries - which ideologically may be opposed to war - are pleased to see him in the trade role. The 49-year-old has a reputation as a tough and hard-working politician. Tipped for the Cabinet, he is expected to be an equal match for Zoellick.

O'Brien was made a Home Office minister in 1997. In this post he famously broke his leg tackling a thief in south London on his way to addressing senior police officers on crime. But it was in 2001 that the MP for North Warwickshire shot to prominence. He controversially revealed that he took a telephone call from Peter Mandelson about the passport application of Srichand Hinduja, a sponsor of the Millennium Dome. Mr Mandel- son, who had been Dome minister, denied recollection of the call. "Hopefully, people will associate me with a bit more than that," says O'Brien bluntly.

In his new post, he straddles the Department of Trade and Industry and the Foreign Office. "There has been a feeling that the person who has done this job is primarily in the Foreign Office. I intend to break down some of those barriers, not only in the way in which I operate, but in the way the officials operate."

His DTI in-tray is already overflowing. On top of the Cancun negotiations there are growing protests from British industry that trade with the US is not on a level playing field. Imports of certain types of steel, for example, are subject to a 30 per cent tariff.

"We must make it clear to the Americans that if they talk about liberal markets then let's have some liberal markets. Let's not have a level of protectionism ... We have got to see some reality," he says. O'Brien indicates that once Cancun is over, he will also raise the issue of US protectionism towards its airlines: "Open skies, except in the US - it is a big issue."

America's main defence of its subsidies and tariffs is that Europe is just as bad with its £30bn-a-year CAP. Last month, year-long talks between EU member states concluded with the promise of some reform of the policy. From 2005, for example, farmers will no longer have to keep a certain number of animals or grow specific crops to qualify for payment. It is hoped that this will spell an end to the famous European food mountains.

Britain, which receives £2.8bn a year in CAP subsidies, was one of the biggest supporters of reform but met opposition from France, which receives £6.5bn. O'Brien says the agreement heralds the start of the "fundamental reform of CAP" as "we have succeeded where, frankly, previous negotiations have failed".

But campaign group War on Want believes the reforms need to go further. "The agreement has been hailed as a great success and the Government is now saying it can go to Cancun with clean hands," says director of campaigns Steve Tibbett. "But it is not good enough - the subsidies remain at the same level. It is difficult for the UK and EU to say they have done a fantastic deal, because they haven't."

But O'Brien says further CAP reform is on the cards. "I very much hope that we can see more movement in the future. We are now set on a new course with CAP. It may take a short time, it may take a long time, but this is the sort of reform we in Britain have been seeking. It is that first crucial step of changing direction that has taken place."

He will be keen to impress this message on his US counterpart tomorrow. Like O'Brien, Zoellick is a tough negotiator. Before America agrees to lift any of its farm subsidies - and, perhaps more critically, agrees to TRIP reform - it needs to believe that Europe is changing too. Much rests on the shoulders of Britain's new trade minister.