The Forum For Democratic Change (FDC) cites what it describes as a lack of democracy as the reason.

On Friday two opposition MPs, Reagan Okumu and Michael Ocula, appeared in court. They are accused of murdering a local official three years ago.

Critics of the government regard the case as politically motivated.

In a letter to diplomats, the FDC says "a temporary suspension of foreign aid may prove to Ugandan President Yoweri Museveni that democracy is the only option and that terror will not be tolerated".

Political manoeuvring

Opposition politicians have strongly criticised the arrests, which the FDC describes as the beginning of a campaign to suppress the opposition ahead of elections in a year's time.

The activities of opposition parties were for years severely restricted in Uganda, in order to end divisions along party and religious lines.

Now as the country looks set to return to multi-party politics, the political temperature is rising.

This is partly because of a campaign to amend the constitution to allow President Yoweri Museveni to stand again - 20 years after he came to power.

Whilst President Museveni's supporters maintain he is still the best man to lead the country, opposition groups complain of increasing dictatorship.

The government says the arrested MPs will receive a free and fair trial.

Members of parliament have called for them to face justice without delay, to dispel the suspicion that the case is intended to sideline the MPs for as long as possible.