London ? After years of study and delay, the British government moved Wednesday to allow Americans and Canadians to bring their cats and dogs into Britain without first having to quarantine the animals for six months.

The plan, to be in place in time for Christmas, would allow those pets to avoid the quarantine provided they meet other conditions intended to prevent the introduction of rabies.

The new rules will also permit British pets returning from visits to the United States and Canada to avoid the long quarantine.

The long-awaited announcement, which follows an easing two years ago of rules restricting the import of pets from Western Europe, came after British scientists concluded that there was little risk of rabies being brought into the British Isles by carefully screened pets.

Instead of the six-month quarantine, which can be traumatic for both pets and pet owners, domestic animals entering Britain will face just a two or three-day isolation period until the new system is perfected.