Vienna - The international Association of Space Explorers (ASE) on Tuesday called on the United Nations to develop strategies against asteroids threatening to hit earth, in a report presented at the United Nations in Vienna.

Among the known 5,600 so-called near-earth objects, and the 500,000 additional ones expected to be discovered in the next 15 years, "several dozen will pose an uncomfortably high risk of striking Earth and inflicting local or regional devastation," the astronauts said in their report.

To counter this threat, the association called on UN bodies and member states to develop a framework for sharing information about dangerous asteroids, and a decision-making mechanism to destroy or deflect them.

Technical capabilities to prevent such collisions with earth already exist, said the ASE, which is comprised of 320 people who have travelled in space.

The options being studied include destroying an asteroid with a large spacecraft or nuclear weapon, or changing its course by using the gravitational force of a spacecraft hovering near the asteroid.

Such strategies would "temporarily put different populations and regions at risk in the process of eliminating the risk to all," for example from impacts of asteroid particles, the report said.

To consider this and other problems before authorizing a mission to avoid a collision, ASE said decision-making structure should be set up soon, in which the United Nations Security Council would have the last say.

The biggest impact from a space object in recent history was the Tunguska event in 1908, in which an meteoroid destroyed 2,000 square kilometres of Siberian forest.