Ehud Olmert, the acting Israeli prime minister, made the comments in an interview with the Jerusalem Post published on Friday.
"Whoever is involved personally and directly in terror is a target," the paper quoted him as saying.
"We haven't forgot that Haniya was an aide to Shaikh (Ahmed) Yassin and Yassin was targeted because he was involved in terror."
Olmert was responding to a question on whether he agreed with a statement from Israel's defence minister that Haniya was a legitimate military target for Israel.
"So if Haniya commits acts of terror, he is opening himself up to the possibility of being targeted. I hope he doesn't," Olmert added.
In a series of interviews in the countdown to Israel's 28 March general election, the acting prime minister made similar remarks in the Yediot Aharonot daily.
"Whoever is involved personally and directly in terror is a target"
Acting Israeli prime minister
Olmert's ruling Kadima party is widely tipped to win the upcoming vote and is keen to deflect any suggestion they are "soft on terrorism".
"All those involved in terrorist attacks are legitimate targets of elimination operations. Remember what happened to Ahmed Yassin and Rantissi who were more important leaders than Haniya," he told the Yediot Aharonot.
Yassin, the spiritual founder of Hamas, and Abd al-Aza al-Rantissi, his successor as Hamas leader, were killed in Israeli air strikes in March and April 2004.
"If he is involved in politics, even politics that I oppose, and not involved in terrorism, he will not be a target," Olmert added.
Haniya has been tasked by Palestinian leader Mahmoud Abbas to form a government following Hamas's surprise victory in a 25 January general election.
Hamas has carried out dozens of anti-Israeli suicide attacks during the course of a five-year Palestinian uprising although none in the past 12 months.