Threat Analysis
The surveys by the US Government indicate that there are:
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A handful of asteroids (10+ km) which can cause mass extinction on the Earth
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A several hundreds of asteroids (1-10 km) which can cause global catastrophe
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A hundred of thousands of asteroids (100 - 1000 m) which can cause regional catastrophe
Because of the difference in their numbers, our civilization will experience impacts by 100-meter asteroids many times (50 is the median number by simple math) before crossing the path with a 1-km catastrophic asteroid*. It is extremely unlikely that our first encounter will be with the 10-km asteroid, for the chances are one in ten thousand.
Currently available proven deflection capability
* Since the Earth's diameter (12,742 km) is so much larger than the asteroid, the size of the asteroids by themselves do not significantly affect the probability of impact. This is similar to the fact that the diameter of bullet does not play major role in accuracy of hitting a target. The number of asteroids is the dominant factor.