EREZ, Israel -- A rocket fired by Hamas militants in the Gaza Strip exploded outside Jerusalem on Friday, opening a new front in fighting between Israel and radical Palestinians and increasing the danger that the conflict will spiral into total war.

Israeli military officials confirmed that rockets that have struck central Israel in the last 24 hours were Fajr-5’s manufactured in Iran and smuggled into Gaza in recent months via the Sinai Peninsula. With a range of more than 50 miles, the Fajr-5 has changed the calculus of the conflict between Israel and Hamas, whose militants previously had been able to target only communities in Israel’s sparsely populated south.

The Fajr brings Tel Aviv and Jerusalem within range of Hamas rocket crews, and Hamas vowed to continue to employ them against Israeli targets.

"We are sending a short and simple message: There is no security for any Zionist on any single inch of Palestine, and we plan more surprises," said Abu Obeida, a spokesman for the Hamas militant wing who uses a nom de guerre to hide his identity.

Israeli military officials warned that the firing of the rockets into central Israel was an “intolerable” situation, even though they’ve yet to cause any damage or injuries. Friday’s rocket landed in an open area in Gush Etzion, a West Bank Jewish settlement about 10 miles south of Jerusalem. On Thursday, rockets fell in the water off a beach and in an open area south of Tel Aviv.

The United States said it was taking steps to tamp down the conflict, though it continued to support Israel’s actions.

“Israel has the right to self-defense,” State Department spokeswoman Victoria Nuland said .

Nuland said Secretary of State Hillary Clinton, who’s in Singapore, had spoken with Israeli Foreign Minister Avigdor Lieberman, Egyptian Foreign Minister Mohamed Kamel Amr and Jordan’s King Abdullah. She said American officials had detected no indication that Egypt, whose new government is close to Hamas, had done anything to undercut its peace treaty with Israel, and she offered a positive assessment of Egyptian Prime Minister Hesham Kandil’s visit Friday to Gaza, where he voiced support for Hamas.

"We appreciate the fact that Minister Kandil went personally to try to ameliorate the situation," she said, calling Egypt’s relationship with Hamas key to a deceleration of the conflict.

“We are urging those countries with influence on Hamas to use that influence to achieve a de-escalation,” she said.

There appeared to be no letup, however, in Israeli preparations for a possible ground invasion of Gaza, perhaps as early as this weekend.

Israeli planes shifted their focus from seeking out rocket launchers to creating corridors through which troops and tanks would move into the seaside strip. As the air force shifted targets, Israeli tanks and artillery units could be seen moving toward the border.

EDITORS: STORY CAN END HERE

“We are creating that corridor, the incursion area for our troops to begin their movement into Gaza when that order is given,” a senior military official in Israel’s southern command told McClatchy, speaking only on the condition of anonymity under the military’s ground rules. “We are expecting to move this weekend.”

Israeli Defense Minister Ehud Barak authorized an additional call-up of soldiers late Friday, adding to the 30,000 reservists who were summoned for duty earlier this week.