The UK's military chief says the troops are on the very edge of the city of Basra in southern Iraq.
Basra is Iraq's second most important city after the capital Baghdad.
It's a very important target for the coalition troops - it's on a route which is 560km from Baghdad and also close to borders with Iran and Kuwait.
Another important development is that Iraq's only deep-water port at Umm Qasr in the south-east has been captured by US and UK troops.
The port is key for bringing in aid for the Iraqi civilian population.