At a news conference after a meeting with Estonia's prime minister, Peres said Israel would not intervene directly in hostilities but would respond to specific requests from Abbas.
"We should help Mr. Abbas in his fight against the terrorists," he said in answer to reporters' questions.
Asked about possible direct measures, Peres said: "We can only respond to Mr. Abbas's requests for help. We will not intervene in the war itself but if Mr. Abbas will request specific help, we will supply [it]."
Peres was in Estonia for the opening of the Baltic state's first synagogue since World War Two.
At least 13 Palestinians were killed in fighting in Gaza on Wednesday, bringing the four-day death toll to at least 37.
Italy offers to send troops to help quell fighting in Gaza
Italy would consider sending peacekeepers to the Gaza Strip if the Palestinian government requested help to end factional fighting, Foreign Minister Massimo D'Alema said on Wednesday.
But D'Alema called for political pressure, including from the Arab world, to end the fighting between Hamas and Fatah.
"If the Palestinian Authority asked for international help to guarantee security in Gaza, that could be considered," he aid. "Still, I believe that at this moment, one must exercise political pressure on the sides that are clashing that are paradoxically part of the same government."
Italy is leading the UN peacekeeping force in Lebanon. D'Alema said last year that if the Lebanon force proved effective, a similar force could be used in Gaza.
D'Alema was speaking after a meeting with Arab League Secretary General Amr Moussa, who also condemned the fighting in Gaza during a joint news conference.
"We should condemn in the strongest terms what is going on in Gaza. But we have to be vigilant and not lose sight of the reasons, the root causes," Moussa said, mentioning poverty and unemployment.
"[This is] a situation that has been imposed on the Palestinians unjustly and unfairly and led to this agitation in Gaza."