Democratic presidential candidate Hillary Clinton says the United States must "stand in solidarity" with European allies after the deadly bombing attacks in Brussels.
Belgian officials say 31 people were killed Tuesday and 187 wounded in two explosions at the Belgium airport and one at a city subway station.
The former secretary of state told NBC News that the U.S. must intensify efforts to prevent terrorism in conjunction with its allies. "We've got to be absolutely strong and smart and steady in how we respond," she says.
But Clinton also said that it is unrealistic to say that the United States can completely shut its borders.
Clinton is campaigning in Washington state ahead of the primaries there tonight.