"In regard to statements that we have been invited, we can only say today that there was some contact from the Polish side," Erekat tweeted.
"Our position remains clear: We will not attend this conference and we reiterate that we have not mandated anyone to talk on behalf of Palestine," he added.
In another tweet on Friday, Erekat also wrote: "The U.S. administration dismissed itself from sponsorship of the peace process because of its decisions that are contradictory to the international law."
In a separate tweet, Hussein Al-Sheikh, a senior Palestinian Authority official, also rejected the invitation, saying that only the Palestine Liberation Organisation could speak on behalf of the Palestinian people.
Poland's Foreign Ministry announced earlier on Friday that Deputy Foreign Minister Maciej Lang had conveyed to Palestine a joint Polish-US invitation to the Middle East conference in Warsaw. The invitation was forwarded to the Palestinian ambassador in Poland, Mahmoud Khalifa.
"Deputy minister #Lang today handed over to Ambassador Mahmoud Khalifa a joint invitation from Poland and the United States for #Palestyna (Palestine - PAP) to participate in the Ministerial Conference on Peace and Security in the Middle East, which will be held in Warsaw," Foreign Ministry wrote on Twitter.
On Wednesday, Mahmoud Abbas, the President of the Palestinian Authority, and the Palestinian Embassy in Warsaw announced that the Palestinian delegation would not attend the Middle East conference in Warsaw.
The embassy wrote in a press release that the Palestinian side believes that talks on the situation in the Middle East should take place in the presence of all the interested sides and on the basis of international law, especially UN and UN Security Council resolutions, and not in order to implement US interests. (PAP)