Washington(CNN) Hillary Clinton congratulated the newly elected mayor of London, Sadiq Khan, in a tweet Saturday morning.
"Son of a Pakistani bus driver, champion of workers' rights and human rights, and now Mayor of London. Congrats, @SadiqKhan. --H" Clinton wrote.
London's mayoral contest made international headlines as race and religion emerged as central issues, as Khan's election makes him the first Muslim mayor of a Western capital city. Clinton's tweet does not mention his religion.
RELATED: London elects Sadiq Khan, first Muslim mayor, after ugly campaign
Islamic extremism is a key issue in the 2016 presidential race, especially after Donald Trump, now the presumptive Republican nominee, proposed in December a temporary ban of all Muslims from entering the United States.
Republicans and Democrats alike denounced the proposal, with Clinton calling the plan "reprehensible, prejudiced and divisive" shortly after Trump's remarks.