The United States special envoy to the Middle East George Mitchell Wednesday night said that Israeli Prime Minister Benjamin Netanyahu and Palestinian President Mahmoud Abbas have discussed complex issues “up front.”

The Israeli and Palestinian leaders Wednesday continued their second round of direct talks at Netanyahu’s official residence in Jerusalem, a meeting lasting close to two hours with Mitchell and U.S. Secretary of State Hillary Clinton on hand.

Netanyahu and Abbas “are tackling up front the issues that are at the center of the Israeli-Palestinian conflict,” Mitchell said in a press conference that followed the meeting.

“The two leaders are not leaving the tough issues to the end of their discussions,” the envoy said, adding that “we take this as a strong indicator of their sincerity and belief that peace is possible.”

Sounding firmly optimistic on the progression of the talks thus far, Mitchell told reporters that the negotiations have “moved very quickly to serious and substantive discussions.”

Mitchell, however, refused to elaborate on the issues that were discussed, citing the importance of confidentiality that both sides have pledged to maintain throughout the negotiations.

According to Mitchell, both Netanyahu and Abbas have agreed that their negotiating teams will meet next week to lay the groundwork for the next round of talks at the leadership level.

After the talks in Jerusalem, U.S. Secretary Clinton is slated to hold a bilateral meeting with Abbas in Ramallah on Thursday and will then depart to Jordan for a meeting with King Abdullah II. Meanwhile, Mitchell is scheduled to visit Damascus on Thursday for a meeting with Syrian President Bashir Assad and Foreign Minister Walid Mualem, to be followed by meetings with top Lebanese and UN officials in Beirut.

In regard to his visits in Syria and Lebanon, Mitchell told reporters that “a part of the (U.S.) objective has been to encourage discussions between Israel and Syria … We do not believe that proceeding on both tracks is necessarily mutually exclusive.”