Hundreds of people gathered in Dallas to protest the killings Thursday night when a gunman opened fire, killing five police officers and injuring seven others.
"The deaths of Alton Sterling in Louisiana and Philando Castile in Minnesota also make clear how much work we have to do to make every American feel that their safety is protected", he said.
Both Trump and Clinton canceled their scheduled events, his in Miami with Chris Christie, hers in Pittsburgh with Joe Biden.
The Clinton campaign says the event will be rescheduled as soon as possible. He said the earlier deaths of two black men in Louisiana and Minnesota were a reminder of "how much more needs to be done" to restore public confidence in law and order.
"Racial divisions have gotten worse, not better", Trump said. He also tweeted a message of support, saying, "Sending prayers and condolences to all of the families devastated by the attack, not only in Dallas, but across the country".
Hillary Clinton pledged Friday to bring law enforcement and communities together to develop national guidelines on the use of force by police officers, days after two black men were killed by police officers. And in moments of national crisis, presidents have shown ability to unify the country, if fleetingly, like George W. Bush did after the September 11, 2001, attacks. The following day, Castile was fatally shot in a auto by a Minnesota officer, with the aftermath livestreamed on Facebook by his girlfriend.
"If Mr. Trump wants to speak to me, I would be happy to brief him on what we're doing".
In an interview on MSNBC, Clinton said Americans "have to be honest, all of us, in facing implicit bias that all of us, unfortunately, may still have". What the Republican Party is going to is find a way to blame Hillary Clinton and liberals for the latest chapter in a growing national epidemic of senseless gun violence deaths.
"Let's put ourselves in the shoes of police officers, kissing their kids and spouses goodbye every day and heading off to do a unsafe job we need them to do", she said.
"Our nation has become too divided". "Crime is harming too many citizens".
Hillary Clinton is widely viewed as more personally qualified and possessing better judgement than Trump, the survey said.
Trump canceled an afternoon event that was set to take place in Miami, Florida.
President Barack Obama, speaking from Warsaw, Poland, called the killings a "vicious, calculated, despicable attack on law enforcement".
Clinton also called local Dallas elected officials and leaders including Dallas Mayor Mike Rawlings and Dallas County Judge Clay Jenkins to express solidarity and condolences, and to offer help, according to an aide.