Upon receiving a notice of a CHANGE order from OWNER and if in the opinion of CONTRACTOR such variant is likely to prevent or prejudice CONTRACTOR from fulfilling any of his obligations under the CONTRACT, he shall notify OWNER thereto in writing and OWNER shall decide forthwith whether or not the same shall be carried out. If OWNER reconfirm in writing his intention to carry out the variations, then the said obligations of CONTRACTOR shall be modified to such an extent as may be justified.