Palestinians walk by buildings destroyed in the Israeli bombardment. AP

Israel bombarded the Gaza Strip as it prepared for a ground invasion it says is aimed at annihilating the Palestinian group Hamas as Russia warned the conflict could spread beyond the Middle East.

In besieged Gaza humanitarian supplies were critically low, as world powers failed to agree on a lull to the fighting to deliver aid, and residents buried the dead in mass graves as the civilain toll mounted.

US President Joe Biden, in remarks looking beyond the war, said on Wednesday that the future should include Israeli and Palestinian states side by side.

Russian President Vladimir Putin warned the conflict could spread beyond the Middle East and said it was wrong that innocent women, children and old people in Gaza were being punished for other people's crimes.

"Our task today, our main task, is to stop the bloodshed and violence," said Putin in a meeting with Russian religious leaders of different faiths, according to a Kremlin transcript.

"Otherwise, further escalation of the crisis is fraught with grave and extremely dangerous and destructive consequences. And not only for the Middle East region. It could spill over far beyond the borders of the Middle East."

Russian President Vladimir Putin attends a meeting. File photo

Reflecting concerns the Gaza war may spread, the Wall Street Journal reported that Israel had agreed to delay invading Gaza until US air defence systems can be placed in the region, as early as this week, to protect American forces.

Asked about the report, US officials told Reuters that Washington has raised its concerns with Israel that Iran and Iranian-backed groups could escalate the conflict by attacking US troops in the Middle East. An Israeli incursion into Gaza could be a trigger for Iranian proxies, they said.

Gaza's war has already sparked conflict beyond the Palestinian territories. Israeli warplanes struck Syrian army infrastructure on Wednesday in response to rockets fired from Syria, an ally of Iran. Israel has also targeted Syria's Aleppo airport and Iranian-backed Hezbollah in Lebanon.

Iran, Israel's arch-enemy, has sought regional ascendancy for decades and backs armed groups in Syria, Lebanon and elsewhere as well as Hamas. It has warned Israel to stop its onslaught on Gaza.

Reuters