According to the office of Israeli Foreign Minister Silvan Shalom he shook the hand of Lebanese President Emile Lahoud at a recent diplomatic event in Tunis.
Lahoud's office, however, denies the event ever took place, saying the account was "based on imagination".
It also rejected a media report that his wife, Andree Lahoud, spoke with Shalom's wife, Judy Nir-Mozes, on the sidelines of the conference.
According to the Israeli foreign ministry account, Shalom was standing near Lahoud as he shook the hands of dignitaries standing close by at a function the Tunisian government put on for delegates to a UN conference, foreign ministry spokesman Mark Regev said.
State of war
"We do not relate any diplomatic importance to this," Regev said, adding that the handshake - whether or not it took place - did not herald any moves towards peace talks with Lebanon.
Lebanon and Israel are in a state of war and the two countries have no diplomatic relations.
Israel occupied a strip of south Lebanon for 22 years until its withdrawal in 2000.
Beirut says Israel continues to occupy a small area of land on Mount Hermon.
Only three Arab states - Egypt, Jordan and Mauritania - have full diplomatic relations with Israel.