WASHINGTON (Reuters/AFP) - The United States on Friday warned activists against plans to send a new aid flotilla to challenge Israel's blockade of the Gaza Strip, saying it would be irresponsible and dangerous. "Groups that seek to break Israel's maritime blockade of Gaza are taking irresponsible and provocative actions that risk the safety of their passengers," State Department spokesperson Victoria Nuland said in a statement, adding that there were established ways to move humanitarian aid to Gaza. "We urge all those seeking to provide such assistance to the people of Gaza to use these mechanisms, and not to participate in actions like the planned flotilla," Nuland said. Israel on Wednesday said it had warned the UN that a new aid flotilla - which activists say could depart from European ports in coming days - could result in "dangerous consequences." Israel has made clear it will prevent any new flotilla from reaching Gaza. A year ago, nine Turkish activists, including one with dual US-Turkish nationality, were killed in an Israeli raid on a similar convoy. The Israeli military came under fierce criticism for the May 2010 raid, which led to a severe deterioration of its ties with Turkey. The United States, Israel's most important ally, has backed Israel's blockade of Gaza, which the Palestinian Hamas group seized from forces loyal to Western-backed Palestinian President Mahmoud Abbas in 2007.