By Taos Turner 

BUENOS AIRES--Union members went on strike across Argentina, shutting down banks, ports and public transportation to demand lower income taxes.

The strike, which is the fourth big labor shutdown President Cristina Kirchner's administration, adds an element of social conflict to Argentine politics as the country prepares for a presidential election in October, said Rosendo Fraga, a historian and political analyst.

Even as the strike was playing out on deserted streets and at abandoned airports and train, plane, subway and bus stations, labor leaders were threatening to holder another, even longer strike if the government doesn't meet their demands.

A heavily unionized nation, Argentina has been through several dozen national strikes over the past 30 years. Powerful labor leaders are credited with helping to take down former President Raúl Alfonsín's crisis-plagued government at the end of the 1980s.

Union bosses don't strike the same degree of fear into government officials as they did in previous decades, analysts say. But labor leaders still hold significant sway over national politics.

Meanwhile, Argentine officials were quick to play down the importance of the strike.

"A very small, insignificant number of [transportation union] workers are affected by the income tax," said Aníbal Fernández, Argentina's presidential cabinet chief. "They're going on strike to defend the high salaries of other unions."

Mr. Fernández said labor leaders aren't giving the government credit for everything it does to boost economic growth, including subsidizing fuel prices to lower costs for transportation companies.

Union bosses complain about high inflation and incomes taxes. While many workers obtain annual wage increases to compensate for double-digit inflation, the salary increases push workers into higher tax brackets, effectively reducing their take-home pay.

Economists say inflation likely totaled close to 40% last year, though government officials say it was just over half that.

"This strike is a product of workers' discontent with government economic policies, which affect income taxes, prices and the loss of purchasing power," said Gerónimo Venegas, the 70-year-old leader of a rural workers union.

With many of the streets and boulevards in this capital city empty and quiet, not everyone was happy about the strike.

"I'm tring to find a taxi because I need to work. I'm tired of these strikes that don't get us anywhere," said Norma Mejurbe, 51, who works at a local court house.

Ms. Mejurbe said she supports Mrs. Kirchner.

"For me, this is a political strike against the government that is being carried out by corrupt union bosses that get rich at the expense of their workers," Ms. Mejurbe said.

Argentine officials, including Economy Minister Axel Kicillof, have so far refused to lower income taxes. That could put them on a collision course with union leaders ahead of October's presidential election. Mrs. Kirchner is barred from seeking a third consecutive term.

Analysts say union bosses are interested not only in getting the government to lower taxes but also in securing the attention of each of the presidential candidates who hope to replace Mrs. Kirchner.

Hugo Moyano, the most influential of Argentina's union bosses, called on the government to act on labor's demands.

"The strike was powerful," Mr. Moyano said at a news conference. "We humbly hope that starting tomorrow those responsible will deal with the needs of our workers and their legitimate demands."

Alberto Messer contributed to this article.

Write to Taos Turner at taos.turner@wsj.com