This has two considerations: interception and destruction.
Interception. A U-2 intercepted the large Chinese spy balloon. Could a modified U-2 employ a weapon to destroy one? A laser is conceivable. But the concept of intercept is alien to the U-2 design, which is difficult to fly even in a deliberately planned intelligence mission. See (USAF) U-2S/TU-2S. Quoting,
…These characteristics combine to earn the U-2 a widely accepted title as the most difficult aircraft in the world to fly.
Not mentioned is that, at altitude, the U-2 flies a coffin corner as narrow as 5 knots, resulting in severe loss of maneuverability.
The classified service ceiling of the U-2 may be adequate for super-pressure balloons, easily identified by the shape, which follows geometric norms, of which the sphere is most common. Zero-pressure balloons, like the NASA “Big 60”, can easily exceed altitudes of practical airplanes. Even the Lockheed A-12 was good for a max of 95,000 feet, at a speed too fast for observation of a nearby balloon.
A short term fix. Close inspection by something like the McDonnell Douglas F-15 Streak Eagle, with high speed camera. Zoom climb is a semi ballistic maneuver that has been used for most fixed wing air-breathing altitude records, when the absolute location is unimportant. Interception would require a specialized guidance package. Kinetic destruction is conceivable, but already obsoleted by laser.
Long term, integration of interception and destruction. Integration of both functions on a commercial derivative jet, flying above the weather. Integration of:
- Upwards facing large aperture telescope.
- Replacement of Sidewinders, unit cost $400K, by laser.
Perhaps JSTARS, slated for the boneyard, could be adapted. Occasional use may not justify a new platform.