In a dramatic reversal, Prime Minister Pierre Trudeau agreed today to postpone his bid to write a new Canadian constitution until he can consider fresh opinions on the controversial matter from the courts and provinces.

The compromise could prove the key to ending Trudeau's bitter and enduring impasse with dissenting provincial governments over the division of powers to be laid out in the constitution.

Or it could open the way for a devastating defeat for Trudeau by the Supreme Court of Canada that would probably end this country's current attempt to bring home its governing charter from Britain, where the constitution now resides as an 1867 act of the British Parliament.

Trudeau wants to send a resolution to Westminster asking it to transfer Canada's charter to Ottawa, installing at the same future amendments in Canada.

The opposition Progressive Conservative Party, which has joined with eight of 10 provincial governments against Trudeau's plan, forced Trudeau into the compromise by blocking final parliamentary debate on the resolution.

To break this logjam, Trudeau agreed to postpone a vote on the constitutional package until the Supreme Court votes on whether it is legal for Trudeau to install a new charter without the provinces' consent.

Leaders of the eight dissenting provinces will confer here April 16 in an effort to present alternative constitutional proposals to Trudeau.

Any agreements that Trudeau and the premiers could work out would be inserted in the constitutional package prior to the final vote by Parliament. That vote is scheduled to take place two days after the Supreme Court announces its ruling on a constitutional case brought before it by Manitoba Province. Hearings in that case will begin April 28.