Iran reaffirmed its backing for the Palestinian resistance against regional arch-foe Israel, the presidency website cited first vice-president Mohammad Reza Rahimi as telling the visiting Hamas premier.
Ismail Haniya arrived in Tehran on Friday on a three-day trip and is due to speak at a rally marking Saturday's 33rd anniversary of the 1979 Islamic revolution, media reported.
"Iran will not retreat one iota from its position on defending the rights of the Palestinian people," Rahimi was quoted as saying, adding that Tehran "will use everything at its disposal to support the oppressed Palestinians."
"A part of God's punishment is on this world, and soon the Zionist regime will be punished for its plots and aggression," Rahimi said, adding: "The Palestinian issue is a red line for us."
Israel views Hamas, the Islamist group that rules the Gaza Strip, as a terrorist organisation and has accused Iran of being its main arms supplier.
Iran has not recognised Israel since the Islamic revolution and backs Palestinian and Lebanese militant groups fighting against the Jewish state.
Tehran has repeatedly voiced opposition to a two-state solution for the Palestinian issue and has put forward its own proposal: a "referendum by (indigenous) Palestinians" regardless of religion but excluding Jews who have immigrated.
The presidency website reported that Haniya "congratulated Iran on the 33rd anniversary of the triumph of the Islamic revolution," and "thanked Tehran's brave stance on the Palestinian issue."
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"We have witnessed the Iranian people's strong support for the oppressed Palestinian people and the resistance of the Palestinians is strong because of such support from Islamic republic," he was quoted as saying.
Media reported that Haniya will meet supreme leader Ayatollah Ali Khamenei, President Mahmoud Ahmadinejad and other senior officials.
Local media said he would also receive an honorary degree from Tehran University.
Khamenei last week called Israel "a cancerous tumour that must be removed, and God willing it will be."
Ahmadinejad, who will give a speech on Saturday marking the day 33 years ago when revolutionaries claimed victory over the deposed regime of the US-backed shah, strongly backs the Palestinian cause.
He has voiced Iran's long-standing policy of rejecting the continued existence of Israel and of supporting its foes, including Hamas.
Hamas this week signed a deal with its secular rival Fatah, which runs the West Bank under Palestinian president Mahmud Abbas, to form a consensus government ruling both Palestinian territories.
Israel has rejected the union, and warned Abbas to choose between reconciliation with Hamas and making peace with Israel.
A senior Fatah official has told AFP that the new Palestinian government would be announced in Cairo on February 18.