By Adam Easton BBC correspondent in Caracas

A strike by managers from Venezuela's state oil company, PDVSA, seems set to worsen after the country's President, Hugo Chavez, announced that seven striking executives had been dismissed.

Executives warn that the country could run out of fuel by the end of the week

The four-day-old partial strike has already begun to affect fuel supplies in the world's fourth largest oil exporter.

Venezuela's labour dispute is Mr Chavez's biggest challenge since coming to power three years ago.

A 24-hour general strike in support of the oil managers on Tuesday has united both the country's unions and business leaders against Mr Chavez.

'Provocation'

Saying the oil managers actions were subversive and bordering on terrorism, Mr Chavez added he would be happy to dismiss all of the company's staff if that was what it took to change the country's leading corporation.

Chavez: Says the country will not stop for anyone

He said during his weekly radio address he had been too soft in the conflict - and after firing seven of the protestors, he said a further 12 had taken early retirement.

Several company executives said the provocation would undoubtedly escalate the industrial action.

They warned that Venezuela, one of the United States' key oil suppliers, could start running out of fuel by the end of the week.

One company refinery has already been closed down, and another is running at minimal levels.

The strike - called to protest against the company's new board of directors - is a potentially massive blow to Venezuela's economy, which relies on oil for more than half its tax revenues and 80% of its export earnings.

Managers say the board has been filled with Mr Chavez's supporters.

Increasing pressure

Mr Chavez's version of events could hardly have been more different. He said workers had begun to start up the stalled refinery and that the industry's operations were completely normal.

The president said the managers enjoyed gross privileges and had a political agenda.

Mr Chavez, whose popularity has slumped recently, is coming under increasing pressure.

The last time unions and business leaders united to strike in December, the country's economy was virtually paralysed.

But Mr Chavez made light of Tuesday's planned strike, saying the country would not stop for anyone.

Pretending to be a football referee, he blew a whistle and declared the groups offside.