ICTSI said in a stock exchange disclosure that shareholders of Portek has until August 10 to decide on its offer. It initially set to close July 20.
ICTSI, however, said its cash offer for Portek of S$1.20 per share was unchanged. ICTSI already owns about 17% of Portek.
Last week, Mitsui & Co. said Portek's majority owners, who control 51.3% of the Singaporean port operator, agreed to accept its higher offer of S$1.40 per share.
Portek operates and manages ports in Indonesia, Algeria, Malta, Gabon and Rwanda.
ICTSI, on the other hand, has operations in 17 countries, including the Philippines.