If an asteroid were on its way to impacting New York City, I think geopolitics would take a back seat and the US government would do whatever it needed to protect its own interests, even at the expense of another country.

And by the same token, even if we did "figure out" the sensitive issues when a tough judgement call had to be made in advance, whose to say it will be honored? Especially if its in the hands of a superpower like the US, a country that doesn't exactly have a great reputation when it comes to playing by the rules.

Countries can barely get along in the best of times, but under the threat of such disaster, I think any political planning would essentially fall apart in the interests of self-preservation...

All that being said, it's still a good idea to think about these issues in advance, to at least be somewhat more prepared to make a decision.

There is a Third Solution

The smaller asteroids are, the harder they are to detect early. If detection methods improve we might get two weeks warning on a 100 meter diameter asteroid. A 100 meter is easily capable of destroying a large city. Nukes are the only way, (using human technology), of fracturing or deflecting an asteroid in a short amount of time. An ICBM is not designed for asteroid interception! They cannot achieve escape velocity with a significant payload without major modification. You would intercept the asteroid far too close to the Earth!

A common misconception is that all Nukes are weapons!

The P.O.N.I. concept uses impact compression, (from hitting an asteroid moving at least 4000 meters per second), to create the supercritical mass for an atomic explosive. It is safe to orbit around the Earth since it doesn't have any heat shielding and won't survive reentry. The design can be inspected and verified by treaties negotiated by diplomats. From high Earth orbit it can respond to an asteroid threat in less than 48hrs.

Given 2 weeks time the already orbiting P.O.N.I. will fire its solid rocket motors and could move to intercept an asteroid at more than a million kilometers. You could send a series of PONIes, with the later ones redirected to get any large pieces from previous detonations. If dust begins to hide the target, send PONIes into the debris cloud. The PONIes will only detonate if they hit something big, and the blasts could clear away the obscuring dust. Shooting blind into a debris cloud is a desperate measure, and that is why I call this tactic The Stalingrad Defense. Stalingrad could also being an example of life after an impact.

The B612 Foundations solution is warm and fuzzy but requires massive energy and material resources that would be better spent on colonization infrastructure.

For further information on the P.O.N.I. See http://www.atoe.com/qdevice.html

It would be a good idea to be ready for any threat however having major nukes flying over head that at any time could lose it's orbit and start to reenter earths orbit or have the system hacked by an enemy and put it where they like does not sound like a great idea to me. We read everyday how secure even the US goverment is. I feel like the percentages of impact from a major asteroid is not in out favor in the long run. Sometimes we are not even aware of the danger till it has passed and is toooooo late. Wormwood.

As far i see, missions early enough to push the
asteroid trajectory away from earth, can avoid an hit,while pushing when only weeks or less would uselessly move hit point across earth but would NOT more avoid overall damage to mankind.
The diverting method applies for enough time
left while the nuclear destruction method
applies when it's too late for rerouting.
I invented the method of pushing the asteroid
with an massive beam of iron balls magnetic
cannon to an safe trajectory.This works
even against debris surrounded comets
because from distant!
The ship needed for such operation gets its power from Seebeck-Nuclid cells which radiate BUT can NOT explode using for example Co60 Electron radiating nuclide within an zirconium hull.The drive consists of an high power ion drive which can intercept
asteroids as fast as 20km per second.
The nuclid core in my conception should
reach constant power of 2MegaWatts for years, which powers enough both drive long timely and push mag- cannon and life support capsule, ship of 20tons.India is most
endangered by asteroids tsunamis: much coast,many people and flat except the northern boundary. They should use their space program for asteroid defense.Payed by
insurances?