Micah Challenge UK, a coalition of Christian churches, organisations and leaders, is calling on Christians to pressure world leaders on their promises to the poor by joining the 'The World Can't Wait' rally in London this weekend.

The rally, to be held on Saturday on the banks of the River Thames, comes the weekend before the G8 leaders meet in Germany to discuss issues including the fulfilment of the Millennium Development Goals agreed in 2000 to alleviate global poverty and its consequences.

The World Can't Wait Rally aims to call on world leaders ahead of the G8 summit to deliver on their promises and take decisive action against poverty and climate catastrophe.

Micah Challenge UK is part of the international Micah Challenge movement of Christians lobbying their governments to do more to ensure the fulfilment of the MDGs to alleviate extreme poverty by 2015.

World leaders signed up to the MDGs in 2000 and to mark the half-way point, Micah Challenge UK has launched the 'Blow the Whistle' campaign to check the half-time scores and keep the UK Government moving on its promises to the poor.

Events on 2 June will kick off for Christians with a Blow the Whistle Worship Service at the Methodist Central Hall in central London, where the acclaimed Tim Hughes will lead worship.

Special guests will include representatives of some of the world's poorest nations as well as the head of Tearfund, Matthew Frost, and the chief executive of World Vision, Charles Badenoch.

Hundreds of Christians are expected to flock to the service, which starts at 11.30am, and nearly eight hundred "early bird" tickets guaranteeing seats have already been snapped up.

After the service, supporters will prayerfully walk to the banks of the Thames, where they will blow their Micah Challenge whistles at 2.30pm. There they will join thousands of other people as they make their own noise with alarm clocks and mobile phones to call on the Government to honour its commitments.

Rev Joel Edwards, General Director of the Evangelical Alliance, a key Micah partner, said: "Christians coming together to demonstrate for the poor shows world leaders the depth of our concern and is also a good witness to people in Britain that the church cares about international poverty."

On 20 May, MPs, top Christian musicians and churches across the UK all took part in events to mark Blow the Whistle Sunday. At the last count 7,819 Blow the Whistle postcards had been sent to Prime Minister Tony Blair, urging him to ensure that the promises the UK Government made to the poor when it signed the MDGs are kept.

Speaking at St Mark's Church in Kennington on Blow the Whistle Sunday, Labour MP for Vauxhall, Kate Hoey said: "The Millennium Development Goals are clearly important and the more pressure that is put on governments all over the world the more chance there is that action will be taken to make them happen by 2015."

At Church.co.uk in central London, musician and activist Andy Flannagan led worship during a Micah Night which included campaigning workshops led by Tearfund and Speak.

Flannagan, who had just returned from 10 days working in an orphanage in Uganda, said: "The night has challenged my heart, mind and body. I've been re-commissioned to give my life to the cause of the poor."

Blow the Whistle is focussing on five key areas - Aids treatment, water and sanitation, climate change, education and trade justice. The Micah Challenge UK coalition includes many Christian organisations like the Shaftesbury Society, the Evangelical Alliance, HTB/Alpha International and Faithworks.