GAZA CITY, Gaza Strip — Hamas gunmen on Tuesday ambushed rival Fatah forces near a key crossing along the Israeli border, killing eight people in the deadliest battle yet in three days of factional fighting.

The incident briefly drew Israeli gunfire, threatening to drag Israel into the conflict at a time when its prime minister said his country was ready to discuss an Arab initiative that offers peace for land.

At least 18 people have died in the fighting, bringing life in Gaza to a standstill and pushing the fragile Palestinian unity government closer to collapse. Hamas and Fatah formed the union to end months of violence.

Tuesday's fighting began when Hamas gunmen approached a training base used by Fatah forces that guard the crossing, officials said. The base was set up in part by a U.S. security team sent to train Palestinians on how to check cargo and bags at crossings.

The Islamic militant Hamas force attacked the base with rockets, rocket-propelled grenades and mortars, said Ahmed al-Kaisi, spokesman for the pro-Fatah Presidential Guard: "We consider this a serious provocation and a crime committed in cold blood."

A jeep full of security men that came under fire veered off the road and crashed. Hamas forces then riddled it with gunfire, said one witness, who gave only his first name, Jamil, out of fear for his safety.

Hospital and security officials said eight men were killed in the ambush.

As the fighting raged, Israeli troops opened fire at two gunmen who approached the border, the army said. Palestinian officials said one man was killed. He was identified as a member of the Presidential Guard, who apparently was trying to help his comrades.

Witnesses also said three Israeli tanks approached Karni, and the Hamas force quickly withdrew. Israel also closed the crossing, which is the passage for cargo going in and out of Gaza.

Israel has remained silent throughout the latest Palestinian infighting, but the border incident illustrated how fragile the situation is. Israel has been debating whether to take large-scale military action in Gaza in response to repeated rocket fire aimed at southern Israel.

In Jordan, Israeli Prime Minister Ehud Olmert said his country was ready to discuss an Arab initiative that offers peace for land.

The plan would give Israel full recognition in exchange for a total withdrawal from lands it captured in the 1967 Middle East war and the creation of a Palestinian state. Israel has welcomed the plan as a good starting point for negotiations, but objects to several provisions.

The Arab peace plan was first floated by Saudi Arabia in 2002 and renewed in March at a meeting of the Arab League. Arab leaders have urged Israel to seize the new opportunity.

Jordan's King Abdullah II told Olmert at a meeting in the seaside resort of Aqaba that Israel first had to take concrete steps to improve relations with the Palestinians.

"The king stressed first and foremost to Mr. Olmert that talking about new settlements or expanding existing ones is in contradiction with Israel's desire for peace," said Amjad Adayleh, spokesman for the palace.

Olmert told the king that reports Israel was to establish new settlements "were baseless," Adayleh said.

He added that Abdullah also urged Olmert to lift an economic blockade on Palestinians.

Adayleh said the meeting focused on the plan and Abdullah told Olmert that "all the Arabs are committed to the peace initiative and they have a real intention for a comprehensive peace if Israel accepts that."

Abdullah also urged Olmert "to set a time frame for making peace with the Palestinians."

Before the talks with Abdullah, Olmert told a conference in Petra, Jordan, of Nobel laureates and Israeli and Arab youth that Israel was ready to listen to Arab views.

"We heard about the Arab peace initiative and we say come and present it to us. You want to talk to us about it, we are ready to sit down and talk about it carefully," he said.

In the West Bank, Palestinian President Mahmoud Abbas urged the immediate implementation of a security plan to halt the internal fighting.

"We must do that ... without any reluctance or delay, to put an end to civil strife and the ghost of internal fighting," he said in a speech marking the anniversary of the uprooting of many Palestinians in the 1948 Mideast War fought over Israel's founding.

The plan calls for rival security forces to operate under a joint command. A majority of the 80,000 security officers in the West Bank and Gaza Strip are loyal to Abbas, while Hamas set up its own 6,000-member militia last year.