Argentina's president will undergo surgery Tuesday to remove blood between her brain and skull that has been causing new and worrying symptoms, her physicians said.

The president's doctors said they had ordered President Cristina Fernandez on Saturday to rest for a month after discovering the subdural hematoma _ a clot inside her skull pressuring her brain and causing headaches. In some patients, such blood clots reabsorb by themselves over time.

But the situation became more urgent after Fernandez felt a weakness and numbness in her upper left arm Sunday evening, according to doctors at the Fundacion Favaloro, one of Argentina's top cardiology hospitals.

“Facing these symptoms, the team decided on surgical intervention,” the hospital's doctors said in a statement Monday.

The surgery involves drilling small holes through the skull to remove old blood.

In a three-paragraph statement released late Saturday that raised more questions than answers, her doctors attributed the injury to a still unexplained blow to her head she suffered Aug. 12. That would have been the day after a primary vote showed a significant drop in support for ruling party candidates, despite her intensive campaigning.

As the 60-year-old leader returned to the hospital for pre-surgical exams Monday, Vice President Amado Boudou made no mention of the planned operation. He said in a speech that top officials would run the country as a team “while she gets the rest she deserves.”

“What Cristina wants is for us to maintain the administration, and to carry on this project that (her late husband and predecessor as president) Nestor Kirchner began and that Cristina has continued,” Boudou said.

What he didn't say, and no other official ventured to guess, was whether Fernandez would formally delegate her executive powers during the surgery, or while she recovered. Boudou is under investigation for alleged corruption and illegal enrichment and currently has one of the worst images among Argentine politicians.

By late Monday afternoon, there was no official announcement about a transfer of power even though some Argentine media reported that immediately after his speech, Boudou signed a document formally assuming control of the government. Questions left by the Associated Press with the president's spokesman, Alfredo Scoccimarro, were not immediately answered.

Even Sen. Anibal Fernandez, who often acts as a government spokesman, told the Telefe channel earlier Monday, “We don't have clear idea what will happen.”

Argentina's constitution provides for, but does not require, a formal transfer of power in case of health problems, said Daniel Sabsay, a constitutional lawyer. A full medical leave would require congressional approval, but short of that, “she alone decides, according to the problem she faces and her doctors' advice, if she needs to delegate some powers to the vice president,” he told Radio Continental.

The president's critics said the government should be more transparent about her health.

The statement issued Saturday night contradicted earlier claims about the nature of Fernandez's hospital tests. During one visit in August that had been described as gynecological, a brain scan was performed that didn't find anything wrong, her doctors revealed.

“There needs to be more information to lower the people's anxiety,” said Fabian Perechodnik, who directs the Poliarquia political consulting firm.

Experts said it's not unusual for symptoms of a chronic subdural hematoma to take weeks to appear, and many patients don't even recall injuring their heads, according to the Mayo Clinic in the United States. The U.S. National Institutes of Health said symptoms can include confusion, decreased memory, difficulty speaking and walking, drowsiness, headaches, and weakness or numbness in the arms, leg or face.

The surgery is considered low risk, and the symptoms can be effectively and safely treated by draining the blood mass through a catheter, according to guidance from the University of Los Angeles.

The president is such an outsized figure in Argentine politics that it's difficult to imagine the government without her at its center. Now she'll be off the campaign trail three weeks before elections that could loosen the ruling party's hold on Congress.

Before Boudou's speech, he and top Cabinet members made a show of unity as they delivered some squad cars to the border police. They were joined by one of the president's would-be successors in the 2015 election, Buenos Aires Gov. Daniel Scioli, and her hand-picked candidate leading the ruling party's congressional slate Oct. 27, Martin Insaurraulde.

Kirchnerism “is more united than ever,” Scioli said. “We want to reassure the people that this team is united and determined.” (AP)