(Adds President Gul, Abbas to visit)
By Ayse Sarioglu and Tulay Karadeniz
ANKARA, July 11 (Reuters) - Turkish Prime Minister Tayyip Erdogan said Israeli bombardment of Gaza was blocking efforts to patch up relations undermined by a 2010 attack by Israeli commandos on a Turkish ship that had been challenging its blockade of the Palestinian territory.
NATO member Turkey and Israel are both U.S. allies and their once close relations, which extended to security cooperation and joint military exercises, were an important part of Washington's regional policy.
"We cannot normalise (relations). First, this cruelty must end," Erdogan said during a speech in the central Turkish city of Yozgat late on Thursday.
"As long as this is not done, it is not possible that a normalisation of the relations between Turkey and Israel be realized," he added, calling for a ceasefire to resume.
Israeli leaders, determined to end Palestinian rocket attacks deep into the Jewish state, have hinted they could order the first ground invasion of the coastal strip in five years.
President Abdullah Gul, speaking to journalists in the Turkish capital after Friday prayers, said such a move would "plant seeds of hatred in the region".
Ankara's recent troubled relations with Jerusalem reached a nadir in 2010 when Israeli commandos stormed the Mavi Marmara, a vessel taking part in an aid flotilla challenging Israel's naval blockade of the Gaza Strip. Ten people were killed.
The Palestinian embassy in Turkey said Erdogan had "expressed sympathy and concern" in a telephone call on Friday with Palestinian Authority President Mahmoud Abbas, and that the two men would meet in Turkey next week.
It also said Turkey had stated it was ready to provide urgent medical and food aid to Gaza and that preparations for an aid delivery were underway.
At least 82 Palestinians, most of them civilians, have been killed in the Gaza offensive, which Israel says is in response to persistent cross-border rocket attacks by Palestinian militants.
Efforts to repair relations between Israel and Turkey had intensified in recent months after Israeli Prime Minister Benjamin Netanyahu apologised for the ship raid and pledged compensation, as part of a U.S.-brokered rapprochement.
Earlier this year Erdogan hinted that the two sides were on the brink of a deal, but progress has been hampered by the decision of a Turkish court in May to seek the arrest of four Israeli military commanders in relation to the killings.
Erdogan, who is running in Turkey's first direct presidential elections next month, has regularly used his vocal defence of Palestinian rights as a campaign platform with his largely conservative Sunni Muslim voter base. (Additional reporting by Ece Toksabay in Istanbul, writing by Jonny Hogg; editing by Ralph Boulton)