Transport unions in Argentina launched a 24-hour strike at midnight Monday over a tax regime they say hurts the lowest earners.
It is the fourth major stoppage against President Cristina Kirchner, who took power in 2007 and completes her second term at the end of this year.
The protest threatened to paralyze bus services, subways, trains, taxis, fuel service stations, airline flights and ports.
Because of the strike the airlines LAN of Chile and TAM in Brazil cancelled flights to and from Argentina.
The government warned that unions had to provide agreed minimum services under collective bargaining agreements or would face punitive consequences.
Unions are angry about a tax system that is progressive -- the more you earn, the higher the tax rate you pay -- but which is constant at low-level incomes.
Late last year the government averted a similar strike by announcing that a Christmas bonus paid to workers would be exempt from income tax.
Leftist parties have said that during Tuesday's strike they will try to block access to Buenos Aires.