The purchase, part of a major ongoing upgrade of the air force's tanker fleet, added weight to concerns that the growing alliance between Israeli Prime Minister Binyamin Netanyahu and Defense Minister Ehud Barak, both hawks on Iran, strengthens the prospect of possible Israeli military action.
The Jerusalem Post reports that the four-engine Boeing aircraft was acquired several months ago and will shortly be flown to Israel where it will be reconfigured by state-owned Israel Aerospace Industries to conduct mid-air refueling operations.
Barak, a former military chief of staff and Israel's most decorated soldier, quit the Labor Party Jan. 17 in a surprise move and formed a new independent party, which he promptly allied with Netanyahu's rightwing coalition.
Barak's abrupt defection was apparently planned in advance with Netanyahu. Labor was a key member of the coalition but its collapse means the right-wingers are no longer constrained by Labor's more moderate ideology.
Barak, by ditching Labor, pre-empted a Labor rebellion by ministers who opposed his policies that would have forced him to resign.
The loss of Labor, which held several Cabinet posts, cut the government's parliamentary majority from 74 to 65 but left Netanyahu with a more united front that did not have to pander to the centrist element.
Netanyahu, a far-right hawk, and Barak, the lifelong socialist, despite their divergent political backgrounds both view Iran's alleged quest for nuclear weapons as a mortal threat to Israel.
They favor military action to ensure the Islamic Republic never challenges Israel's nuclear monopoly in the Middle East.
Their recent appointment of the hard-charging Lt. Gen. Yoav Galant as military chief of staff, Israel's top general, has bolstered their hawkish position. Galant also favors taking on Iran.
Aluf Benn, veteran commentator of the liberal daily Haaretz, reported Jan. 18 under the headline "Military strike on Iran is what unites Netanyahu and Barak," that Netanyahu needs Barak's military credentials to buttress his efforts to neutralize the Iranian threat.
"Without Barak by his side, Netanyahu would find it hard to advance aggressive moves on the Iranian front," Benn observed.
"Netanyahu has no military record that grants him supreme defense authority, as Ariel Sharon had. Only Barak, with his rank and medals, his seniority as a former prime minister, can give Netanyahu this kind of backing."
Netanyahu's hard-line position was made more emphatic after the outgoing director of the Mossad, Israel's foreign intelligence service, took the unusual step of taking a busload of Israeli journalists to a secret location for a three-hour briefing in which he asserted that Iran wouldn't able to produce a nuclear weapon before 2015 and that an Israeli assault would be disastrous.
That undercut Netanyahu's position on Iran and his insistence on urgent efforts, including military action, by the United States and its allies to defang Iran.
Netanyahu quickly ordered the director, Meir Dagan, whose clandestine efforts are credited with slowing Iran's nuclear progress, to publicly retract his statements.
In this context, the enlargement of Israel's aerial tanker fleet, however modest, has strategic implications.
The size of that fleet, a pivotal element in any air assault on Iran and one that will determine the scale of such attacks, is classified.
But the International Institute for Strategic Studies, a prestigious London think tank, lists nine tankers -- four B-707 and five KC-130H Hercules aircraft -- in the 2010 edition of its annual "Military Balance."
The Israelis asked the Americans two years ago for more tankers but were rebuffed, apparently because Washington wanted to discourage any Israeli action against Iran.
Whether the 707 sale indicates a change in U.S. policy isn't clear.
But the Israeli air force is understood to be waiting to see which aircraft the U.S. Air Force selects for its next generation of tankers before buying additional aircraft.
The Israelis have considered converting U.S.-manufactured Gulfstream business jets into airborne tankers but abandoned that idea.
"However, future plans include the possibility of large unmanned aerial vehicles being used as refueling aircraft," The Jerusalem Post reported.
"Unmanned refueling tankers would minimize the risk to pilots and be harder for enemy radar to spot because they are relatively small."