This is a foolish thing to do.

You can only have a discussion towards a good end with an enemy if you are flexible and you demonstrate amity.

Doing this:

https://www.aljazeera.com/news/2018/07/accuses-north-korea-illegally-smuggling-oil-products-180712161217886.html

will leave Kim Jong-Un with a suspicious mind that the US does not really have any measure of goodwill for its welfare.

If you cut off oil to a nation you cripple a nation.

A country that does this to you is a country that harbour's animosity towards you. 

This more than sufficient evidence to remain prepared and be on guard.

Therefore, restart the nuclear program and the missile program.