BERLIN (Reuters) - U.S. Secretary of Defense James Mattis and Homeland Security chief John Kelly will attend the Munich Security Conference in February, and the event’s organizers said on Wednesday they expect other senior U.S. officials to attend also.  Mattis and Kelly were confirmed in their posts just days ago, following President Donald Trump’s Jan. 20 inauguration.  “All signs point to a particularly strong participation of both the new administration, as well as Congress,” the group said in a statement.     Bavarian state premier Horst Seehofer had invited Trump to visit Munich - and possibly the annual security conference - shortly after his election in November, although U.S. presidents have not attended the event in the past. U.S. vice presidents, by contrast, have frequently attended the annual event in Munich, which draws leaders and diplomats from Europe, the Middle East and the United States. U.S. Vice President Mike Pence has been invited but it was not yet clear if he would attend, a spokesman said.  Wolfgang Ischinger, a former German envoy to Washington and the conference’s chairman, said participants would address issues such as the future of transatlantic relations, NATO and the EU, the Ukraine crisis, ties with Russia and the war in Syria. On Jan. 15, Trump said NATO was obsolete because it had not defended against terror attacks but that the military alliance was still very important to him. “I hope that we will not mince words and speak honestly about our disagreements as well as about our common interests and values,” Ischinger said in a statement. Other confirmed participants include U.N. Secretary General António Guterres, European Council President Donald Tusk, EU High Representative Federica Mogherini, NATO Secretary General Jens Stoltenberg, the presidents of Poland, Ukraine, and Afghanistan, and the prime ministers of Norway, Hungary and Iraq. Russian Foreign Minister Sergei Lavrov will participate, as well as Sigmar Gabriel, who will take over as German foreign minister on Friday. Many business leaders, defense and foreign ministers, lawmakers and representatives of non-governmental organizations such as Human Rights Watch also take part.   