The convoy of lorries made their way down the M4 from Carmarthenshire
Hauliers have threatened to blockade refineries if their fuel price protest, which saw a slow convoy along the M4 in west and south Wales, does not succeed.
The two-mile convoy of more than 150 lorries travelled from west Wales to Cardiff on Tuesday to protest at fuel costs.
Organisers say they want fuel duty to be cut within seven days.
Both the UK and assembly governments said they understood the pressures brought by rising fuel costs.
The Treasury said it was addressing the situation.
Prime Minister Gordon Brown and Chancellor Alistair Darling will meet leaders of the oil industry in Scotland on Wednesday morning to discuss ways of increasing production.
The convoy in Wales on Tuesday was part of a day of fuel price protests across the UK, including a convoy which headed to Downing Street.
Plans to head to the Welsh assembly in Cardiff Bay to hand in a petition were changed after negotiations with police.
The organisers of the Welsh protest said haulage firms were being driven to the wall by the high cost of diesel and a planned two pence rise in fuel duty.
The convoy stretched for two miles along the M4
They are calling for an "essential user" rebate of between 20 and 25 pence per litre for HGV drivers.
Organiser Mike Greene said the hauliers are giving Gordon Brown a deadline of a week to cut fuel duty by between 20 to 25 pence per litre - or they will blockade refineries.
Speaking on the BBC News Channel, Mr Greene claimed hauliers across the country feel the same.
The protest, which was over by mid-afternoon, saw M4 eastbound traffic at a standstill or crawling along at about 5 mph as hauliers drove from Carmarthenshire.
A maximum of 50 vehicles entered the Cardiff West services car park at junction 33 of the M4 after an agreement was reached with the hauliers to avoid going into the city.
A petition was handed to Nick Bourne, leader of the Conservatives in the Welsh assembly, and Tory AM and transport spokesman Andrew RT Davies.
After the protest, South Wales Police said a driver from the convoy was issued with a warning for a public order offence after leaving his vehicle on the motorway and urinating on the hard shoulder.
People will have to stop working sooner or later because there's no point working for a loss
Martin Arthur, owner of haulage firm
Martin Arthur, 54, who was at the services and who owns a haulage firm in Usk, said: "The cost of diesel is going up almost every day. We're just handing all our money over.
"People will have to stop working sooner or later because there's no point working for a loss."
Dave Lasky, of Bob Gay Plant Hire, Llantwit Fardre, said: "I wanted to come today because I'm only 24 and it's affecting me more than the older guys.
"I've got other bills to pay, and I've to pay for my car. Something has to be done or I will lose my job."
A Treasury spokesperson said fuel prices had risen by more than 19% since this time last year.
The spokesman said: "To respond to short-term pressures, the 2008 Budget announced that the 2p per litre fuel duty increase, scheduled for 1 April, will be deferred until 1 October."
The assembly government said: "The price of fuel - and the duties imposed on it by the UK government - are not the responsibility of the assembly government.
The spokesman said, however, the issue would be raised with the UK government because of the impact on the haulage industry, transport services and individual motorists in Wales.
Mike Childs, Friends of the Earth's Head of Campaigns, said despite fuel price rises, the overall cost of motoring has gone down in real terms - but the cost of public transport has risen.
He said: "Rising oil prices and the impending threat from global climate change mean the government must take urgent action to ensure our addiction to oil doesn't set us on the road to ruin.
"Government must fast track investment in public transport and backing for smarter cars that use less petrol so our society is not held to ransom by our reliance on a dwindling and insecure natural resource," he added.
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