KHAN YOUNIS, Gaza Strip (AP) — Israel and Hamas have completed the sixth exchange of hostages and Palestinian prisoners with just over two weeks remaining in the initial phase of their fragile Gaza ceasefire. And U.S. Secretary of State Marco Rubio has landed in Israel to begin a Mideast tour. Israelis expressed relief Saturday as the three hostages appeared to be in better condition than the emaciated ones freed a week ago. The ceasefire faces major challenges with its first phase concluding in early March. There have not been substantive negotiations over the second phase, in which Hamas would release all remaining hostages in return for ending the war.