I rented to a foreign government and now they are refusing to pay their portion of Real Estate Taxes. Do i have any recourse?

Generally, a foreign government would be exempt from U.S. taxes. The question is whether a foreign government can be made to pay whatever it has agreed to pay for. This would be an issue under the purview of the US Foreign Sovereign Immunities Act, which precludes foreign governments from being sued unless a specific exception applies. An attorney can study the lease and analyse the facts to see if an exception applies.

As my colleague stated, a lot depends on the expressed terms of the lease agreement, and what available remedies you have to enforce said agreement. Best of luck to you.

As others have stated, the lease is an important document to be reviewed.
I can understand the consulate's position if the lease required it to pay real estate taxes.
You would have a stronger case If your lease said the consulate had to pay as additional rent its pro-rata share of the real estate taxes. In this case, the consulate is being charged rent and not the real estate taxes.