Retirement tax questions

@vishmir --  

I am assuming you are a U.S. citizen.

Here is the exact wording of Article 18 (5) (a):

5. a) Where a citizen of the United States who is a resident of the United Kingdom
exercises an employment in the United Kingdom (emphasis mine) the income from which is taxable in
the United Kingdom and is borne by an employer who is a resident of the United
Kingdom or by a permanent establishment situated in the United Kingdom, and the
individual is a member or beneficiary of, or participant in, a pension scheme established
in the United Kingdom,
(i) contributions paid by or on behalf of that individual to the pension
scheme during the period that he exercises the employment in the United
Kingdom, and that are attributable to the employment, shall be deductible (or
excludable) in computing his taxable income in the United States;

https://home.treasury.gov/system/files/131/Treaty-UK-7-24-2001.pdf

All I can do is cite for you the information that I believe is relevant to your situation.  What you do with that information is of course up to you.