Zimbabwe's government has applied to the Supreme Court to overturn the acquittal of opposition leader Morgan Tsvangirai on treason charges.
Mr Tsvangirai still faces another treason charge
In October, Mr Tsvangirai, leader of the Movement for Democratic Change (MDC), was cleared of plotting to kill President Robert Mugabe.
The charge of treason could have brought a death penalty on conviction.
The justice minister had initially said his government would respect the judgement.
But the country's attorney-general now says the government has formally requested leave to appeal the decision.
Secretly taped video
"We have applied to the Supreme Court for leave to appeal the acquittal," said acting Attorney-General Bharat Patel.
"I have no idea when this will be heard but there is no reason why it should not be this year," he added.
Morgan Tsvangirai was cleared of plotting to assassinate President Mugabe and seize power ahead of 2002 presidential elections.
Mr Tsvangirai, who lost the election, had accused Mr Mugabe of stealing it.
The case against him centred on a secretly-taped video of a Montreal meeting between him and a Canada-based political consultant, Ari Ben-Menashe.
Prosecutors said Mr Mugabe's "assassination" was discussed during the meeting.
But the defence team said the grainy tape was doctored as part of a plot to entrap Mr Tsvangirai.
The judge ruled that treason could not be proved beyond reasonable doubt.
Mr Tsvangirai, currently in the UK to gain support ahead of next year's parliamentary elections, still faces a court case arising from another charge of treason.
His second treason trial next month relates to his call last year for street protests to oust President Robert Mugabe.