"Because our leaders are weak, I said this was going to happen - and it is only going to get worse," Trump said in a statement, Reuters reported on Monday.
"I am trying to save lives and prevent the next terrorist attack. We can't afford to be politically correct anymore,” he added.
Earlier, US President Barack Obama denounced the Orlando shooting as an act of terror and hatred, and ordered the American flag lowered to half mast to honor the victims.
“Today as Americans we grieve the brutal murder, a horrific massacre of dozens of innocent people,” Obama said during a White House address to the nation.
“Although it is early in the investigation, we know enough to say that this was an act of terror and an act of hate,” he added.
Trump's campaign said he will address the attacks in a speech he already had scheduled to deliver on Monday addressing national security and responding to criticism from Democratic rival Hillary Clinton.
The mass shooting also left 53 others injured.
The gunman, identified by US media as a Daesh (also known as ISIL and ISIS) sympathizer named Omar Mateen, a US citizen of Afghan descent from Port St. Lucie, Florida, took hostages at the club and barricaded himself in the complex but was later killed by specially trained SWAT units.
The suspect reportedly called 911 moments before the attack, pledging allegiance to the terror group, citing a federal law enforcement official.
Daesh later on claimed responsibility for the attack, according to media outlets affiliated with the Takfiri group.