The Movement for Democratic Change has gone to court to try to force out the result of the March 29 vote, saying its leader Morgan Tsvangirai has won and should be declared president, ending the 28-year rule of President Robert Mugabe.
Mugabe is trying to delay the result announcement, pending a recount, to give him time to prepare for a probable runoff against Tsvangirai.
George Chikumbirike, a lawyer for the Zimbabwe Electoral Commission, told judge Tendai Uchena: "It would be dangerous in my view to give an order because it might not be complied with ... because of outside exigencies which the party (ZEC) will be unable to control."
He did not elaborate but appeared to be referring to rising tension in Zimbabwe because of the post-election impasse.
Chikumbirike also declined to say how far the ZEC had gone in preparing to announce the result, saying this was privileged information which "the commission has entitlement to release when it's ready".
Jacob Zuma, leader of the ruling party in Zimbabwe's powerful neighbour South Africa, earlier joined a chorus of demands for the release of the results.
The MDC says Mugabe, accused by critics of ruining his once prosperous country, has unleashed a wave of violence against the opposition since the election and called on African nations to intervene to prevent further bloodshed.
Zuma, who rivals President Thabo Mbeki as the most powerful man in South Africa and is the frontrunner to succeed him in 2009, told the Star newspaper: "I think the Zimbabwe Electoral Commission should have announced results by now."
Western powers led by former colonial ruler Britain and the United States have been calling for the result since last week but South Africa has much greater influence as the regional power that has tried to mediate in the Zimbabwe crisis.
"It is not a good thing to keep the nation in suspense. Now the Zimbabwean elections have become an international issue. We all expected that once the elections were finished, results would be announced. Now there are suspicions from the people," said Zuma, who met Tsvangirai earlier this week.
His remarks opened a gap with Mbeki who has consistently called for "quiet diplomacy" in Zimbabwe and led unsuccessful mediation last year by the regional body SADC.
Zuma ousted Mbeki as party leader in December and has gradually begun to eclipse him since then.
The third candidate in the presidential election, ruling party defector Simba Makoni, also called for the results to be released.
"We don't know what is going on, but the results must be released without any further delay," said Makoni, a former finance minister.
He said his officials had been denied access to the vote counting centre and the delay was causing national tension.