A delegation from Hamas, headed by its leader Khaled Meshaal, arrived in Tehran on Sunday as part of a regional push to reinforce support for the Palestinian group after the Israeli invasion of Gaza.
Hamas was in close contact with Iran, its main backer along with Syria, during the 22-day Israeli offensive against Gaza, which was halted last month, with the two sides declaring separate ceasefires.
Khamenei said the war in Gaza had yet to be finished, praising "the resistance of Gazans".
"The Islamic resistance (Hamas) should be prepared for any possible situation, including a fresh war in Gaza," Khamenei told Meshaal, Fars reported.
"The enemy's (Israel) psychological war … still goes on."
Israeli and U.S. officials have accused Iran of providing weapons, cash and training to Hamas militants in Gaza. Iran insists it only gives moral and political support to Hamas. Meshaal praised Iran for backing Hamas, Fars reported.
"The Islamic Republic of Iran has a big share in our victory in the Gaza Strip," said Meshaal, who also met Iranian President Mahmoud Ahmadinejad.
Iran's Foreign Minister Manouchehr Mottaki called for the immediate lifting of Israel's blockade of Gaza.
"The Gaza blockade should be lifted and Gaza port and the crossings should be reopened for reconstruction," state television quoted Mottaki as saying during a joint news conference with Meshaal.
Hamas views the war as resulting in regional diplomatic gains for the group, with Turkey criticising Israel and Qatar convening a high-profile meeting with the participation of Hamas that supported Hamas's objectives.
Meshaal visited Qatar last week. Five other Hamas politburo members are accompanying Meshaal on the visit to Tehran.
Hamas said it would intensify its post war diplomatic efforts to lift the Israeli blockade on the Gaza Strip, imposed with the help of Egypt.
The group has kept a line open with Cairo, which is mediating a deal for a more solid truce that tries to meet Israel's demands for stopping arms flows into Gaza and Hamas's demands for lifting the blockade.
Hamas regards the blockade, which damaged Gaza's economy and further impoverished the majority of the territory's population, as a form of illegal collective punishment and cited it as a reason for not renewing a ceasefire with Israel in December. (Writing by Parisa Hafezi)
