The Central Government may, on the basis of the preliminary findings recorded by the designated authority, impose a provisional duty not exceeding the margin of dumping :

Provided that no such duty shall be imposed before the expiry of sixty days from the date of the public notice issued by the designated authority regarding its decision to initiate investigations :

Provided further that such duty shall remain in force only for a period not exceeding six months which may upon request of the exporters representing a significant percentage of the trade involved be extended by the Central Government to nine months.