Argentine President Cristina Fernandez will be operated on for thyroid cancer on Wednesday, her supporters having lined up outside the hospital since the night before with signs saying Strength Cristina.

The government last week announced her diagnosis of papillary carcinoma, detected during a routine medical checkup just before Christmas. Doctors say the 58-year-old Fernandez has a better than 90 percent chance of recovery.

The diagnosis sparked sympathy in a country where Eva Peron, wife of former leader Juan Peron and known as Evita, is revered decades after dying of cancer at the age of 33.

Like Evita, Fernandez is loved for her efforts on behalf of Argentina's poor. Supporters, who rallied around Fernandez after the 2010 death of her husband and predecessor as president Nestor Kirchner, started congregating on Tuesday outside the hospital where the operation is scheduled for 8 a.m. (1100 GMT)

Wildly popular among Argentines who benefit from her generous welfare spending, the president often gets bad marks from business leaders who say her interventions in the economy frighten off investment.

She is one of several left-leaning Latin American leaders to have cancer. Venezuelan President Hugo Chavez, who underwent chemotherapy last year, speculated after the Fernandez diagnosis that the U.S. empire may have developed a way to give the illness to its political rivals.

Paraguayan President Fernando Lugo's lymphatic cancer is in remission and former Brazilian leader Luiz Inacio Lula da Silva is being successfully treated for a tumour on his larynx.

VOTES, HIGH HEELS

A talented orator fond of glamorous clothes, high heels and make-up, Fernandez still wears black as she mourns Kirchner.

Many thought his death spelled the end of the couple's idiosyncratic blend of state intervention, nationalist rhetoric and the championing of human rights. But Fernandez won re-election in a landslide last October, helped by brisk economic growth fuelled in part by hefty grain export revenues.

Having secured a second four-year term with 54 percent of the vote, she promised to stay true to her policies despite complaints from Wall Street and international investors over her unorthodox approach to the economy.

Argentina is a grain exporting powerhouse, supplying almost half of the world's soyoil, used for cooking and for making biofuels. It is just as strong in soymeal, used to feed cattle, as well as providing 20 percent of the world's corn.

At a time of heightened tensions with the country's most powerful union leader, Hugo Moyano, the cancer diagnosis helped quell rumblings of a transportation workers strike over year-end bonus demands.

The work stoppage would have hit the grains sector as most of the country's agricultural goods are taken to port by truck.

(Reporting By Hugh Bronstein; Editing by Eric Beech)