"Look, these are some very serious times, and the safety of the people attending the convention, the employees, their family members, the people in the city of Houston, have their public health concerns," Turner said. "First responders, police, fire, and municipal workers will all be in contact or in close proximity to this indoor gathering. Simply, the public health concerns outweighed anything else."
WATCH: Mayor Turner's emotional moment on saying no to GOP convention
Turner said the contract cancellation will mean that the convention cannot be held at the George R. Brown Convention Center or any other facility in Houston, but may continue virtually.
"I am the mayor of every single person in this city, and if you're not willing to step up and do the right thing, I am not going to divorce my responsibility and my child. We closed down the Houston Livestock Show and Rodeo, and this convention is no greater or better," Turner said.
During a virtual City Council meeting Wednesday, Turner said he asked the city's legal department to work with the Houston First Corporation, which operates the George R. Brown Convention Center, to review the contract with the state party.
"Where there are provisions that would allow us to cancel this convention - we will exercise those provisions," Turner said. "And the plan is to exercise those provisions to cancel this agreement, this contract, today - to not go forward with this convention."
TAKE A LOOK: Cancellation email from the city of Houston and Houston First
During Wednesday's news conference, Turner also addressed the protests that were held in Houston after the death of George Floyd.
"If you want to march outside, you can do that. That's your First Amendment right. You don't need a permit from me," Turner said.
Turner said since the GOP convention is an indoor event, people were going to be in a close proximity and social distancing would be challenging.
The news comes days after Turner threatened to cancel the convention if it violated COVID-19 rules.
As of Wednesday, the city of Houston reported 204 new COVID-19 new cases, according to Turner, although he mentioned he believes there may be some sort of "glitch" in the state's system and believes the number is higher.
With the number of people getting infected by the virus and no cure in sight, for the first time, the Texas Medical Center announced they have entered Phase 2 for ICU beds, according to Houston City Council.
Additional reporting by ABC13 found that David Persse with the Houston Health Department shared in a letter that "the planned use of the George R. Brown Convention is a clear and present danger to the health and well-being of attendees, workes, local hotel workers and restaurant owners."
In response to Turner's directions, the Texas Republican Party Chairman, James Dickey issued the following statement:
"This morning at the Houston City Council meeting, Mayor Sylvester Turner stated that he will do all he can to cancel the Republican Party of Texas State Convention. After allowing tens of thousands of protesters to peacefully assemble in the same city, in the same area, without any of the safety precautions and measures we have taken, he is seeking to deny a political Party's critical electoral function that should be equally protected under the constitution. Mayor Turner had the authority to shut down the convention, until he actively took steps - as reported by the Houston Chronicle on June 30 - "removing his own authority to cancel it." the statement read.
"With his words today, Mayor Turner is saying Houston does not want business. He does not want Houston to get back to work. He is not able to move forward and rise to these new challenges. Is the City of Houston never going to get back to work? Is the City of Houston never to hold another convention at their cavernous Convention Center? This is an opportunity to show how to get back to work safely and how to hold conventions safely with cutting edge technology. Our legal team is assessing the ability of the City to act at this time in this manner and weighing our legal options. We are prepared to take all necessary steps to proceed in the peaceable exercise of our constitutionally protected rights," Dickey wrote.
The Greater Houston Partnership president and CEO Bob Harvey also released a statement:
"We thank Mayor Sylvester Turner for taking the necessary steps to cancel next week's in-person state GOP convention. As a number of organizations including ours have voiced in recent days, Houston simply cannot accept the risk that comes with hosting an indoor event for thousands of participants from across Texas at a time when COVID-19 is surging in the community. We believe this move will protect the health and safety of both the delegates and the hotel and convention center employees who were scheduled to work the event, as well as protect the public at large. By making this decision today versus next week, the Republican Party of Texas can now finalize arrangements to host this important event in a virtual format."
Harris County GOP released the following statement in regards to the cancellation:
"Mayor Turner's hypocritical flip flop on public gatherings is a political stunt. While he joined in massive marches in the streets last month, he has now blocked Republican grassroots activists from peaceably assembling even under the most stringent health safeguards. The Mayor should not abuse power for political ends." - Harris County Republican Party Chairman Paul Simpson
Mayor Turner threatens to shut down Republican convention if they violate COVID-19 rules