It was the latest sign that Abbas, the front-runner in the race, plans to reach out to Israel after Sunday's election, despite a series of recent hard-line speeches and campaign appearances with Palestinian gunmen.
In other developments:
"After the elections, we will start negotiations," Abbas told a news conference in Nablus, the West Bank's largest city.
Asked whether Sharon is a partner, Abbas said: "Ariel Sharon is an elected leader and we will negotiate with him. We will put the road map on the table and say that we are ready to implement it completely," he said.
The road map, a peace plan calling for the establishment of an independent Palestinian state, has been stalled for more than a year.
"I can't say that Ariel Sharon is not a partner, but whether or not he is serious, we will explore it," he added.
Abbas told the Israeli daily Maariv that his first order of business after next week's election is to seek a renewal of peace talks and to start cleaning up the Palestinian security forces. "We will begin a dialogue with the Israeli side to see if there is willingness to renew the process," he said.
The Israeli reserve officers, meanwhile, wrote that the planned withdrawal "is totally illegal" and that soldiers must not participate in it. The officers belong to a West Bank brigade that is largely made up of Jewish settlers.
The letter is the latest sign that widespread insubordination could accompany the Gaza pullout. Jewish settler leaders have warned that hundreds, and possibly thousands, of soldiers could refuse orders to dismantle settlements.
Lt. Col. Yitzhak Shadmi, one of the officers who signed the letter, said the officers were asking the army not to involve them in the withdrawal. In an interview with Army Radio, he was evasive when asked whether he would refuse orders if the army did not comply. He said thousands of soldiers identify with his views.
In response, Yaalon summoned the officers for questioning. "Any officer who continues to express the views stated in the letter will be dismissed from his duty and expelled from the Israel Defense Forces," Yaalon said in a statement.
Sharon warned Wednesday that the government would act with "all its might" against military dissenters and hard-line protesters who attack soldiers. His comments were prompted by a confrontation earlier this week between settlers and soldiers trying to dismantle an unauthorized West Bank settlement outpost.
Justice Minister Tzipi Livni was to meet with legal experts Thursday to discuss available tools in prosecuting extremists. The meeting is a prelude to a larger meeting of judicial, government and security officials in the coming days.
On Wednesday, Attorney General Meni Mazuz ordered a police investigation of settler leaders Daniella Weiss and Noam Livnat, who have urged soldiers not to participate in the dismantling of settlements.
Weiss told Army Radio on Thursday that the attorney general is Sharon's "lackey" and that the judicial system is not independent.
In the past two decades, small groups of left-wing soldiers have also refused to serve, including during Israel's occupation of southern Lebanon and in the West Bank and Gaza Strip.
Sharon is determined to push ahead with the Gaza withdrawal, which marked a sharp turnaround for the prime minister who once was one of the most vocal champions of Jewish settlements.