At the summit of the 57-member Organisation of the Islamic Conference, the world's largest Muslim organisation, Abbas appealed to leaders from Muslim countries for support at a critical stage in the Middle East peace process.
A draft declaration to be adopted by the leaders "backs Palestine, and condemns Israel for what it is doing in Gaza", said Riad Malki, the Palestinian Authority foreign minister.
In Washington, US State Department spokesman Sean McCormack dismissed President Abbas's accusations as "an example of overheated political rhetoric", and urged the Israelis and Palestinians to "keep their focus on the political process".
The two sides today resumed high-level talks with a US representative, Lieutenant General William Fraser, the first to take place at senior level since talks were suspended at the start of the month in protest at Israel's recent invasion of the Gaza Strip.
Israel has faced criticism from the US over the continued construction of settlements in the occupied West Bank, which it has described as "unhelpful" to the peace process. The Ha'aretz newspaper quoted an unnamed Israeli official as saying: "Real tension has developed with the Americans, and if there are no steps on the ground we will find ourselves in big trouble."
Fraser will also have to confront the recent escalation in violence between the sides, which has strained the US-backed peace talks.
Yesterday, Islamic Jihad launched a volley of rockets at southern Israel from Gaza, after Israeli undercover forces killed four of its fighters in the West Bank.
Renewed conflict began at the end of last month as Israel's blockade on Gaza entered its eighth month.
The fighting intensified as Hamas launched long-range missiles at the Israeli city of Ashkelon, provoking an invasion of Gaza by Israel in which at least 107 people were killed.
Last Thursday, a Palestinian gunman opened fire in a Jewish seminary in Jerusalem, killing eight students.
Ehud Barak, the Israeli defence minister, said the conflict would intensify before calm was achieved. Referring to Israel's raid in the West Bank, Barak said it "proved once more that Israel will hunt down murderers with Jewish blood on their hands".
With George Bush due to visit the region in two months, international pressure for a political solution is likely to increase.