Haniya, speaking to reporters before attending talks in Gaza between factions intended at defusing tensions, said: "Civil war is a term that does not exist in the Palestinian dictionary. I assure the people that these incidents can be overcome."
Clashes have intensified between Hamas and Fatah since the Islamist-led government deployed a new 3,000-member paramilitary unit last week.
A cabinet spokesman said the government would not disband the force despite demands from Abbas, the president and head of Fatah.
Fears of civil war
The battle for control of security in Gaza has raised fears of civil war, which could cripple the Palestinian Authority and strengthen Israel's position to impose final borders with the Palestinians unilaterally, in the absence of peace talks.
But most analysts point out that tensions so far have only involved gunmen bickering over control issues and that the Palestinian population at large is unlikely to be drawn into a civil war.
Moreover, the Israeli occupation of the Palestinian territories has been a uniting factor over the years.
"Civil war is a term that does not exist in the Palestinian dictionary. I assure the people that these incidents can be overcome"
Palestinian prime minister
The new Hamas militia battled gunmen from a Fatah-dominated security service in Gaza on Monday in fighting that killed a Jordanian diplomat's driver and wounded several other civilians.
There were two botched assassinations attempts at the weekend against Abbas' top security men, one of whom was seriously injured at the weekend.
Though Hamas said it was innocent, many believed it or its smaller rival, Islamic Jihad, planted the explosive.
Abbas, who unlike Hamas is committed to peace talks with Israel, said after meeting the Israeli foreign minister for the first time in months on Sunday that civil war was "the red line that nobody dares cross."
He also pledged to start an internal dialogue between factions. But Fatah officials have said tensions would not stop unless the Hamas security force disbanded.
Hamas took power in March after trouncing the long-dominant Fatah in parliamentary elections in January. Hamas is formally sworn to Israel's destruction but has largely abided by a truce in attacks on Israelis for the past 15 months.
Haniya said the talks on Tuesday among Hamas, Fatah and other factions would focus on building unity.
Hamas and Fatah gunmen clash
regularly on the streets of Gaza
Ghazi Hamad, cabinet spokesman, said: "He is calling on all parties to show restraint and not to use weapons at the expense of dialogue."
But Hamad said the government was committed to keeping the "back-up force" because its aim was to end chaos in Gaza, an impoverished seaside territory of 1.4 million people.
Maher Meqdad, a Fatah spokesman in Gaza, said failure to quell internal violence would give the Israeli prime minister, Ehud Olmert, a "free hand to continue with his unilateral plans" to reshape the occupied West Bank.
Olmert wants to annex settlements blocs built on occupied West Bank land and set his country's permanent borders.
He will meet the US president, George Bush, on Tuesday and is expected to discuss plans for the West Bank.
Jordan's representative to the Palestinian Authority, Yahya al-Qarala, whose driver was killed on Monday, urged Palestinians "to be rational" and halt the clashes.
"These are not useful but on the contrary destroy the Palestinian achievement made in the last 10 years," he said at a funeral in Gaza for his driver, referring to Palestinian self-rule under the 1993 Oslo accords.
Meanwhile, the Palestinian foreign minister, Mahmoud al-Zahar, left Gaza on Tuesday for a trip to East Asia to try to obtain funds and bolster political support for the new government.
He will visit China as well as mainly Muslim nations Malaysia and Indonesia.