Q: Unlocked iphone bought in US to be used in Israel

As long as it is officially unlocked and not hacked it should work but you may not be able to use LTE depending on the model of the iPhone.

Get the model number to verify the LTE Support as mentioned by Deggie, and make sure you have contact info for the Reputable vendor in case Activation Lock comes into play.

http://support.apple.com/kb/PH13695

http://support.apple.com/kb/TS4515

Also keep in mind you will not have warranty coverage or service support from Apple...the coverage is only valid in the country the iPhone was to be sold in.  If that matters to you keep it in mind buying in the US for use elsewhere.

That is the Label that is in the E=Bay ad?  or what.  Those ads can SAY anything.  Just trying to prevent you from taking home an expensive brick.

Contact the cell provider you plan to use and see if that is compatible with their LTE bands.

http://support.apple.com/kb/HT4627 for iPhone Wireless Carrier support and features.

http://www.apple.com/iphone/LTE/ for iPhone Model numbers and covered LTE bands.