The Sir Galahad, a Royal Navy auxiliary ship, on Friday docked at Umm Qasr with 650 tonnes of aid, including food, medicine and fresh water, after the Royal Marines claimed to have cleared a narrow path in the Persian Gulf leading up to Iraq's only deep-water port.
The Sir Galahad was supposed to dock on Wednesday, but got delayed due to storms and discovery of mines.
The United Nations' World Food Programme has said it would need more than $1 billion to feed Iraqis for six months.
It has also warned of a humanitarian disaster in Iraq if aid does not reach the people very soon.