He called it one example of how the US can support the Jewish state in the aftermath of the Iran nuclear deal.
Carter visited Hussein Lookout, with a sweeping view of the border as well as the Golan Heights, in an effort to emphasise US concern about a range of threats that face Israel.
These include tens of thousands of short-, medium- and longer-range Hezbollah rockets and missiles in southern Lebanon that could hit Israeli villages and cities.
Carter hit the same theme later at a joint news conference in Tel Aviv with Israeli Defence Minister Moshe Yaalon.
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They used the appearance to make a public show of unity at a low point in US-Israeli relations heavily strained by Israeli's opposition to the Iran deal.
The agreement, reached between US-led world powers and Iran, puts limits on Iran's nuclear program in exchange for lifting crippling economic sanctions on the Islamic Republic.
Yaalon warmly praised Carter's track record of support for Israel, while acknowledging the split over the Iran deal. "We greatly disagree when it comes to the agreement with Iran and fear for the future in the aftermath of its signing," Yaalon said.
"Yet we discuss this issue in a fully open manner, alongside many other issues of great importance.