BOGOTA, Oct 28 (Reuters) - Colombia's state-controlled oil company Ecopetrol on Friday replaced the head of its board of directors, just one day after his appointment, hitting its already-weak peso currency.

Finance Minister Jose Antonio Ocampo told reporters on Friday that Carlos Cano's appointment the day before had been "premature" because the board had not finished its meeting when the announcement was made.

The appointment of Cano, the longest-serving board member, was reversed after President Gustavo Petro opposed the decision, according to two sources with knowledge of the talks.

Saul Kattan, an economist educated in Colombia and the United States, was appointed on Friday, after being nominated by Petro to join Ecopetrol's board earlier this week.

Petro said on Twitter that Ecopetrol "configures its board of directors like any other company, following share holding." "The majority of shares are the state's," he added.

Colombia owns more than 88% of Ecopetrol.

Ocampo said there was no negative perception of Cano and that he was technically not removed from the post because his appointment had not been finalized.

Citigroup said in a note to clients that the move "sends the wrong message and challenges the board of directors' independence, which may justify investors risk aversion that has translated into an implied equity risk for Ecopetrol."

Citigroup said Kattan was elected as board chief in a split decision.

Though Ecopetrol shares were up 3.9% on the Colombian stock exchange to 2,410 pesos (about $0.50) per share on Friday, the peso fell 0.26% to 4,835 pesos per dollar after three days of gains from a historic low on Monday.

Sergio Olarte, chief economist for Colombia at Scotiabank, said the Ecopetrol move hurt the peso. "Definitively it was relevant," he said.

The currency has fallen on Petro's comments on capital controls and criticism of the central bank's interest rate increases as well as uncertainty over a $4 billion tax reform proposal.

The government said on Thursday it may change its position on prohibiting new contracts for oil exploration.

Olarte said Ecopetrol was "already in the market's sights because of the issue of whether new contracts will be signed or not." (Reporting by Bogota newsroom, writing by Marianna Parraga; Editing by Cynthia Osterman)