(Reuters) -Donald Trump selected U.S. Senator Marco Rubio to be a Secretary of State, sources said on Monday, putting the Florida-born politician on track to be the first Latino to serve as America's top diplomat once the Republican president-elect takes office in January. By selecting Rubio for a key policy role, Trump may help consolidate gains among Latinos and make clear that they have a place at the highest levels of his administration. The Ukraine crisis will be high on Rubio's agenda. Rubio, 53, has said in recent interviews that Ukraine needs to seek a negotiated settlement with Russia. During Trump's 2017-2021 term, for instance, Rubio co-sponsored legislation that would make it harder for Trump to withdraw from the North Atlantic Treaty Organization, by requiring two thirds of the Senate to ratify withdrawal.