The latest letter, whose first signers are Texas Republican Ted Poe and Michigan Democrat Gary Peters, calls on President Barack Obama to "unequivocally reiterate that the United States stands behind its longtime friend and ally" and to block any condemnation or investigation at the United Nations.

"Israeli forces used necessary force as an act of self-defense and of last resort," says the letter, labeling the passengers who battled the Israeli commandos "extremists who sought to aid the Iran-backed terrorist Hamas regime."