Washington ? The government on Monday recommended a speed limit for commercial ships along the Atlantic coast, where collisions with the endangered right whale threaten its existence.

About 300-400 of the whales are left in the wild, and they migrate annually between their southeastern Atlantic breeding grounds to feeding areas off the Massachusetts coast, intersecting busy shipping lanes.

The head of the National Oceanic and Atmospheric Administration said Monday the new limit, the first to be instituted on the East Coast for a marine creature, was needed to assure its survival. The rule would set a speed limit of 11.5 miles per hour (10 knots) within 23 miles (20 nautical miles) of major mid-Atlantic ports and throughout the whale’s breeding and feeding areas. The new regulation would cover ships 65 feet or longer and expire in five years if not renewed. Boats from federal agencies would be exempt.

“The bottom line is that this critically endangered species needs our help,” said retired Navy Vice Admiral Conrad C. Lautenbacher, the agency’s administrator.

But the latest version of the so-called ship strike regulation differs from a draft released more than a year ago that was delayed in part because of objections from Vice President Dick Cheney’s office and White House economists over the accuracy of the science linking ship speed to whale deaths.

“NOAA’s decision on these measures is based on the best data and scientific understanding available,” White House environmental adviser James L. Connaughton said Monday.