Zahar, who served as Palestinian foreign minister in the government Hamas formed in Gaza after winning elections in 2006, also said Hamas had asked Egypt to let it import 1,000 containers into Gaza for use as temporary housing for Palestinians displaced during the Israel Defense Forces campaign, which ended in mid-January.
A group of Hamas engineers arrived in Cairo on Monday to study the purchase of the 1,000 containers.
Hamas has also asked Egypt to press Israel to let wood, glass, aluminium, steel and electrical supplies into Gaza to rebuild what was destroyed in the offensive, Zahar said.
Israel has restricted supplies of building materials to Gaza, saying some of them might help Hamas rearm and earn the movement credit with Palestinians living in Gaza.
Zahar added that Palestinian officials, backed by the United States, were obstructing the dialogue due to open between Palestinian groups in Cairo on Wednesday.
"There are people who want this dialogue not to take place because they will lose their positions and their privileges," he told Reuters in an interview in the Egyptian town of Ismailia, where he was visiting his wife's Egyptian relatives.
Zahar repeated Hamas complaints that Fatah has detained dozens of Hamas members in the West Bank in the past week. "These matters [the arrests] do not serve dialogue," he said, adding that "there are U.S. [intelligence] agencies working in the West Bank."
The arrests have added to the tension between the two largest Palestinian groups during preparations for the dialogue.
Zahar, who was visiting his wife's Egyptian relatives in Ismailia, also rejected Fatah complaints about arrests by Hamas in Gaza.
"We have published pictures of what they call political detainees in Gaza. These are people who have confessed that they provided the enemy [Israel] with information about where fighters were stationed and the tunnels [to Egypt] and the type of weaponry," he said.