Well, nothing is set on stone.
Anyway, it is a bit too ambitious, a bit too soon.
I am unsure how it works in the United States, but could he start 'working' and use it as an excuse to b re-elected? Maybe his plan is not to build it in this term but the next one(s).
In itself, I think this type operation should be done with a lot of time and planning, The costs are just way too much for one nation to do it.
Then again, I don't know much, so I may be talking no-sense.