Before his plea bargain agreement, Tappin had denied attempting to sell batteries for surface-to-air missiles which were to be shipped from the US to Tehran via the Netherlands.
He was originally thought to have faced up to 35 years in jail if found guilty.
His guilty plea, to one count of the indictment, calls for a 33-month sentence which prosecutors have said they will not oppose him serving back in the UK.
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Jean-Louis Cayrou, 54, was found guilty of murdering his ex-lover Patricia Wilson, 58, after their relationship broke down.
Both the pilot and the passenger died in the collision shortly before 5pm near Shaw Lane, Shifnal near Telford.
Councils have been warned not to use instruction leaflets after accusations that they appear to promote the 'In' campaign.