The BBC's Charles Haviland in Colombo says the general has been in talks with Sri Lanka's opposition coalition about the possibility of his running for president against Mr Rajapaksa.
Opposition politicians say that resigning from his post as army chief would clear the way for him to stand as a presidential candidate.
But in an interview with BBC Tamil, Gen Fonseka would not be drawn on reports he might enter the presidential race.
"I am retiring. That's all I can say at the moment," he said.
COLOMBO, Sri Lanka — Sri Lanka's top general, who led the battle to crush the Tamil Tiger rebels and ended the island's 30-year civil war, has resigned from his post, an official said Thursday.
Gen. Sarath Fonseka's resignation comes amid growing media reports that he is planning to contest the next presidential election as an opposition candidate, challenging incumbent President Mahinda Rajapaksa. Fonseka has not confirmed the media reports.
An official from the president's office said his secretary received Gen. Fonseka's resignation letter Thursday. A source close to Fonseka said he has sought approval to retire from the force effective Dec. 1.
Both sources asked not to be named due to the sensitivity of the issue.
As army commander Fonseka masterminded the battle against the Tamil rebels. Soon after the war's end in May, he was promoted to chief of defense staff, a largely ceremonial post.
The government announced last month that it would call early elections for president and parliament, aiming to take advantage of its popularity after crushing the rebels. Dates have not been set.
Opposition parties early this month formed an alliance to contest the elections, saying their main aim is to scrap the powerful presidency and increase the say of parliament under a prime minister.
Retd. Chief of Defence General Sarath Fonseka in his final address asked politics be kept out of the Army, noting the significance absence of the three armed forces at his fairwell ceremony. Presently He’s meeting with the President Mahinda Rajapaksa.
Retired Chief of Defence Staff General Sarath Fonseka waving to the crowd after his farewell ceremony at the Army Head Quarters. Pic by Sanka Vidanagama
The outgoing Chief of Defense Staff General Sarath Fonseka is seen here waving at onlookers at his farewell ceremony held at the Army head quarters this morning. Pix by Pradeep Dilrukshana
President Mahinda Rajapaksa had a meeting with the SLFP district leaders and the heads of political parties in the ruling coalition today to discuss strategies for a major election. The President however did not say what election would be conducted first.
A Minister who participated in the meeting told Daily Mirror on condition of anonymity, that no one asked about it either. The President had instructed party organizers to start political work in view of a major election in their respective electorates from today.
President Mahinda Rajapaksa had a meeting with the SLFP district leaders and the heads of political parties in the ruling coalition today to discuss strategies for a major election. The President however did not say what election would be conducted first.
A Minister who participated in the meeting told Daily Mirror on condition of anonymity, that no one asked about it either. The President had instructed party organizers to start political work in view of a major election in their respective electorates from today.
Sri Lanka to hold presidential poll first - minister
Sri Lanka's will hold presidential elections, probably in mid-January but ahead of a parliamentary poll, a senior cabinet minister said on Monday, ending weeks of speculation over which would be held first.
"The president has informed all the party leaders now and he has signed the proclamation," said the cabinet minister, who declined to be identified.
The Eastern Province’s largest Tamil political party, now with the UPFA Government, said yesterday it would not campaign for President Mahinda Rajapaksa at the upcoming Presidential Election.
The decision was taken by the Tamil Makkal Viduthalai Pulikal (Tamil People’s Liberation Tigers) headed by Eastern Province Chief Minister Sivanesathurai Chandrakanthan alias Pillayan on Friday night.
“Thirteen of our 15 politburo members who took part in the meeting supported this move,” TMVP General Secretary Edwinsilva Kailasaraja told the Sunday Times. The meeting took place at the party office at Lake Road in Batticaloa and the members discussed the issue for almost three hours to arrive at this decision, he said.
Mr. Kailasaraja said te TMVP was not in a position to go to the people in the East and ask them to vote for Mr. Rajapaksa.
During the 18 months in office, he said, Chief Minister Chandrakanthan had been prevented from carrying out any development work or giving jobs to people in the East. “Hence, we have nothing to tell our people,” he said.
The decision not to support President Rajapaksa was taken though the UPFA controls the Eastern Provincial Council (EPC), holding 20 of the 35 seats. That includes six members of the TMVP who contested the last EPC poll on the UPFA ticket.
Mr. Kailasaraja accused the Provincial Governor Mohan Wijewickrema of obstructing the work of the Chief Minister. He said on two occasions they had written to President Rajapaksa on the matter. Even letters written to the Governor were not getting a response.
Gov. Wijewickrema, however, denied the allegation. Officials at the Governor’s office said Rear Admiral (retd.) Wijewickrema, with the approval of President Rajapaksa, provided 200 jobs for minor employees.Last week, the TMVP attempted to veto the financial allocations budgeted for the Governor in a bid to force him to quit. However, two TMVP councillors opposed the move and helped approve the allocations by a majority vote.