Thousands of striking truckers and other union members have gathered in front of Argentina's presidential palace to demand tax cuts in a one-day work stoppage seen as a challenge to President Cristina Fernandez.
The strike was called by Hugo Moyano, the head of the powerful General Labour Confederation union, who was once a close ally of Ms Fernandez and her late husband, former president Nestor Kirchner. Mr Moyano's support helped Fernandez win re-election in October.
But their relationship has soured in recent months, and their ongoing spat culminated in Wednesday's strike, the first time the labour federation, an umbrella group for numerous unions, has called a strike since Nestor Kirchner took office in 2003.
"It wouldn't cost Mrs President anything to ... talk to workers," Mr Moyano told his supporters at the rally in Buenos Aires. He added that he hoped Ms Fernandez would "realise that she can't continue with this overwhelming haughtiness".
Despite the impressive crowd that streamed into the Plaza de Mayo, where Mr Moyano made a rousing speech urging Ms Fernandez to dialogue with workers, the effect of the strike was limited. Public transit workers including bus and taxi drivers did not take part, meaning that traffic in Buenos Aires and other cities was largely unaffected.
Ms Fernandez was not in Buenos Aires on Wednesday. She travelled to a village in central San Luis province to inaugurate a pig-raising facility. She has repeatedly asked unionists to rein in their demands during a global financial downturn that is hurting the Argentine economy.
In addition to truckers, who union officials say took part in the strike almost unanimously, garbage collectors, newspaper and food distributors, some rural workers, as well as employees of the health and textile sectors walked off the job.
Mr Moyano and the strikers are demanding the state cut back income taxes to improve wages amid inflation, which private analysts estimate at about 25% a year. They are also demanding better treatment from the executive branch.
Mr Moyano is a gruff, former trucker who is reviled by middle- and upper-class Argentines.