The trial was earlier scheduled to open Monday.
The trial involves the former President of MRND party, Mathieu Ngirumpatse, ex-party Vice-president, Edouard Karemera, and former Secretary General, Joseph Nzirorera.
The Chamber ordered the postponement due to unavailability of witnesses for Karemera, who will be the first to present his defense. The tribunal's administration can only arrange arrival of the witnesses after March 17.
In addition, the chamber noted that the former MRND vice-president had still not communicated the necessary identification elements of his witnesses to the prosecutor.
The postponement was also necessary because one of the principal counsels for the defense will not be available from 26 March until 6 April, the judges stated in their ruling.
Meanwhile, the tribunal on Friday rejected Nzirorera's motion to replace the three judges of the trial, whom he had accused of biasness towards the prosecution. It was turned down on grounds that the accused had not advanced any presumed impartiality of the trial chamber judges.
Lead attorney for Nzirorera, Peter Robinson, accused the judges of having hidden from him secret requests from the prosecutor, which directly made accusatory statements about the defense.
The trial which started in September 2005 is considered as among the most important before the ICTR. It may stretch beyond the set deadline of the UN Security Council of December, 2008 for all first instance trials.
According to UN estimates, about 800,000 ethnic Tutsis and moderate Hutus were killed in the July-April 1994 slaughter.
© Hirondelle News Agency