JERUSALEM — A Hamas leader has asked President Obama to engage with his militant movement, rather than marginalize, it in a letter that was passed through United Nations officials in Gaza to Senator John Kerry, Democrat of Massachusetts, during a visit there on Thursday. Mr. Kerry said Friday that he did not know the letter’s contents and had given it to the American Consulate in Jerusalem so it would be sent to the White House. But the letter’s author, Ahmed Yousef, the Hamas deputy foreign minister, said by telephone that it was a two-page document urging the new administration to...