Zimbabwe's ruling Zanu-PF party has given its backing to President Robert Mugabe's participation in a possible run-off vote.
The party's top leaders met to decide how to react to election results that have yet to be announced, six days after the presidential poll.
The opposition MDC claims its leader received enough votes to win outright.
There had been speculation that Mr Mugabe would stand aside rather than face a second poll.
Zanu-PF also said it would call for recounts for 16 seats in the parliamentary elections.
If successfully contested, these would be enough for the party to regain the majority it lost for the first time since 1980 in Saturday's poll.
'Dear old man'
Zanu-PF administration secretary Didymus Mutasa said there would be a re-run in the presidential race if the election commission "compels us".
"We are down but not out," he said after the five-hour meeting.
"Absolutely the candidate will be Robert Gabriel Mugabe - who else would it be other than our dear old man?" he said.
The MDC (Movement for Democratic Change) says its candidate, Morgan Tsvangirai, took 50.3% of the vote, just over the 50% needed to avoid a run-off.
An independent projection says Mr Tsvangirai gained 49%, just below the threshold, with Mr Mugabe on 42%.
The MDC said it had filed a suit at Harare High Court, demanding the release of the official results.
Correspondents say there are fears a second round - which would be expected to take place within three weeks - could lead to a resurgence of the violence and intimidation that has been a characteristic of past elections in Zimbabwe.
The BBC's Peter Biles says that Zanu-PF hardliners backed the move to endorse the 84-year-old leader if a run-off is called.
But the ruling party remains divided, he says, with many who would still like to see a change of leadership, knowing that under Mr Mugabe, Zimbabwe has no future.
On Friday, hundreds of Zanu-PF supporters - some of them veterans from the war against white rule that led to independence - marched through the capital, Harare, the Associated Press news agency reported.
Jabulani Sibanda, head of the Zimbabwe War Veterans' Association, which has been associated with past election violence, said Zanu-PF lost the elections because "people were pushed by hunger and illegal sanctions".
"Under current circumstances the spirit of our people is being provoked. We will be forced to defend our sovereignty," he said.
Mr Mugabe's former information, Jonathan Moyo, who is now an outspoken independent MP in parliament, said the ruling party was seeking ways to reverse its losses.
"War veterans and militias" would "terrorise the villagers", he warned in an interview with French news agency AFP.
Police said two foreign nationals arrested at a hotel on Thursday had been charged with practising journalism without accreditation.
One has been named as Pulitzer Prize-winning New York Times journalist, Barry Bearak. The other is said to be a British citizen.
But the attorney general said there was no case against two foreign journalists, their lawyer said, although he added that he did not know if they would be released.
Another US citizen, a staff member at the US-based National Democratic Institute, was detained at Harare's airport on Thursday, the organisation said.
Also on Thursday, the MDC said its offices in Harare were ransacked. It denied that Mr Tsvangirai had gone into hiding and said he was "safe".
Mr Mugabe, 84, came to power 28 years ago at independence on a wave of optimism.
But in recent years Zimbabwe has been plagued by the world's highest inflation, as well as acute food and fuel shortages, which correspondents say have driven many voters to back the opposition.
So far, 10 of the 60 Senate results have been officially announced, with each party taking five seats.
In the lower house of parliament, the MDC took 99 seats, while Zanu-PF won 97. A smaller MDC faction, which backed former Mugabe loyalist Simba Makoni in the presidential election, won 10 seats, leaving them with a potentially influential role.
However, Zanu-PF gained 46% of the vote in the parliamentary race, against 43% for the MDC, which supporters of Mr Mugabe say gives him hope of victory in a run-off.