* "Clear evidence" of Israeli war crimes in Gaza -Malki
* Israel warns of retaliation for any ICC action against it
* Lack of Palestinian, Israeli membership hinders ICC action
* Hamas could oppose Palestinian Authority bid to join ICC (Specifies Palestinians' upgraded status at UN, adds context)
By Jussi Rosendahl and Anthony Deutsch
THE HAGUE, Aug 5 (Reuters) - Palestinian Foreign Minister Riad al-Malki said there was "clear evidence" of war crimes by Israel during its offensive in Gaza as he met International Criminal Court prosecutors on Tuesday to push for an investigation.
Malki visited The Hague shortly after Israel and the Palestinian Islamist Hamas movement that dominates Gaza entered a 72-hour truce mediated by Egypt in an effort to secure an extended ceasefire.
Last week, the United Nations launched an inquiry into human rights violations and crimes alleged to have been committed by Israel during its offensive, given the far higher toll of civilian deaths and destruction on the Palestinian side.
"Everything that has happened in the last 28 days is clear evidence of war crimes committed by Israel, amounting to crimes against humanity," Malki said. "There is no difficulty for us to show or build the case. Evidence is there for people to see and collect. Israel is in clear violation of international law."
Israel said it did its utmost to avoid civilian casualties in Gaza but accused Hamas of putting its people in harm's way by launching rockets from within densely populated districts.
Malki told reporters that the Palestinian Authority (PA) wanted to give the ICC jurisdiction to investigate alleged crimes by both sides in the Gaza conflagration and that he had discussed a timeline with prosecutors to join the court.
Unless the Palestinians do so, no investigation is possible.
Malki said the PA's current status at the United Nations, upgraded to "non-member state" from "entity" by a vote of the General Assembly in 2012, qualified it to become an ICC member and a decision on whether to apply could happen "very soon".
But he pointed to possible complications by saying this could go ahead only with the cooperation of Hamas, which is shunned by the West as a designated terrorist group and is a strong political rival of the Western-backed PA, which governs only in parts of the West Bank not occupied by Israel.
By joining the court, the Palestinian territories would automatically open themselves up to war crimes both committed by adversaries and by themselves within their borders.
"We want really to be assured that if we undertake that decision (for ICC membership), then all Palestinian factions adhere to that decision and know in advance its consequences and ramifications," Malki said.
"If it (includes) action committed by Palestinian groups (against Israelis), then we are ready to accept that. But nothing compares to the atrocities, the carnage, committed by Israel," he added, accusing Israel of destroying schools, hospitals and water grids in Gaza during its incursion.
HAMAS COULD OPPOSE ICC MEMBERSHIP
Analysts say Hamas was unlikely to agree to ICC membership if it meant the possibility of its leaders being prosecuted in The Hague for what they consider legitimate defence against Israeli occupation.
The hardline Islamist Hamas regards all of Israel as well as Palestinian territories as occupied land, unlike the PA which seeks a state on land - the West Bank, Gaza and East Jerusalem - captured by the Jewish state in the 1967 Middle East war.
Israel and Hamas traded accusations of war crimes during the Israeli air and ground onslaught on Gaza, during which Islamist militants fired thousands of rockets into the Jewish state. Most of the rockets were shot down by Israel's Iron Dome missile shield or landed in open, uninhabited areas.
Both sides defended their military operations as consistent with international law.
Israel declined public comment on Malki's remarks. But a senior Israeli official who asked not to be identified said any ICC legal action against Israel over Gaza would prompt an Israeli counter-suit at the ICC against the Palestinians.
As neither Israel nor the Palestinians are ICC members, the court lacks jurisdiction over Gaza. This could be granted by a U.N. Security Council resolution, but Israel's main ally, the United States, would probably veto any such proposal.
The overwhelming General Assembly vote recognising the "non-member state" of Palestine was strongly opposed by the United States and Israel due to the lack of a peace agreement. The latest round of U.S.-brokered peace negotiations between Israel and the Palestinian Authority collapsed in April.
Membership of the ICC opens countries to investigations both on their behalf and against them. Several major powers, including the United States, as well as Israel have declined to ratify the court's founding treaty, the Rome Statute, citing the possibility of politically motivated prosecutions.
The ICC, created more than a decade ago to prosecute individuals for war crimes, is a court of last resort, meaning that it will only intervene when a country is found to be unwilling or unable to carry out its own investigation. (Additional reporting by Dan Williams in Jerusalem, Nidal al-Mughrabi in Gaza and Michelle Nichols at the United Nations; Editing by Mark Heinrich)