Updated

Fighting for his political life, Bogota's leftist mayor convened supporters for a Friday rally to battle his dismissal, an ouster that some believe could hurt attempts to make peace with the Americas' most powerful leftist rebel group.

Gustavo Petro, a former rebel-turned-politician, wasn't just fired this week. He was also barred from elected office for 15 years by Colombia's inspector-general, a conservative ally of former President Alvaro Uribe.

Petro had alienated many since taking office last year with a high-handed, aloof style, and the inspector-general accused him of overreaching constitutionally. But he is a national figure, an anchor of the democratic left, and thousands of people were expected to rally in protest on Friday.

As a senator, Petro led investigations that uncovered collusion between killer far-right militias and Uribe allies, helping send dozens of officials to prison, and he finished fourth in 2010 presidential elections. He had been a militant with the M-19 rebel movement, whose 1990 peace pact is considered an inspiration for the government's current talks in Cuba with the Revolutionary Armed Forces of Colombia, or FARC.

After Monday's announcement of sanctions against Petro, the FARC questioned how its members would be treated if they reach an accord.

It issued a statement that the measure is "a serious blow" to the government's credibility in year-long negotiations that have so far led to partial, confidential agreements on land reform and rebel political participation.

The U.S. ambassador-designate to Colombia, Kevin Whitaker, was worried as well. He said at his Senate confirmation hearing on Wednesday that if Colombians interpret Petro's ouster as meaning the left won't be allowed to freely participate in the country's political life "the basic conditions for peace are going to be in some ways eroded."

Inspector-General Alejandro Ordonez ousted Petro not for alleged corruption — the case for his predecessor, who is now on trial — but for trying to fire private contractors in a bid to overhaul garbage collection in the capital. The attempt backfired as fetid piles of garbage amassed over three days before the mayor caved.

Still many doubt that Petro's ouster has weakened Colombian democracy or threatens peace, even if they disagree with the ruling.

That's the opinion of Antonio Navarro Wolff, a former M-19 rebel who has held nearly every political post available in Colombia, from congressman to mayor to Cabinet minister.

"What we have is a punishment that doesn't fit the crime," said Navarro Wolff, who quit in frustration as Petro's chief of staff last year after just three months on the job.

To keep his job, Petro must file an appeal to Ordonez. There is no other constitutional recourse, and a final ruling could take some weeks.

In the meantime, Petro has appealed to the Inter-American Commission of Human Rights in Washington to issue an immediate stay barring Colombia from removing him. He was expected to travel there on Tuesday to meet with the commission's president.

Despite the controversy, there is no indication that Ordonez's job is threatened. Elected by the Senate — with support from Petro — he has already sentenced dozens of elected officials from all sides of the political spectrum to political purgatory.

No other country save Venezuela has an office with such broad powers, said Rodrigo Uprimny, who heads the think tank DeJusticia.

Some are questioning those powers, however. Chief Prosecutor Eduardo Montealegre and the justice minister, Alfonso Gomez Mendez, are among powerful Colombians calling for review of the institution.

President Juan Manuel Santos has said nothing beyond issuing a statement Monday saying he "respects" Ordonez's decision and "laments" any inconveniences it would cause.

___

Associated Press Writer Frank Bajak in Lima, Peru, contributed to this report.