Safeguard duty extension permitted where imports from a foreign source cause market disruption, allowing continued imposition after industry adjustments. The substituted proviso authorises the Central Government to extend the imposition of safeguard duty where imports from a foreign source continue to cause or threaten market disruption; the government may so act notwithstanding measures taken by the domestic industry to adjust, and may continue the duty beyond the initial period of imposition subject to an outer limit measured from the date the safeguard duty was first imposed.