President Trump told Republican lawmakers Thursday that "sometime this year," he will announce a "substantial tax cut for middle-income folks who work so hard."

"We are working on a tax cut for the middle-income people that is going to be very, very inspirational," the president told House Republicans at their annual retreat in Baltimore. "It's going to be something that -- I think it's what everyone's really looking for."

Thursday's visit marked Trump's first trip to Baltimore since insulting the city in a series of July tweets, calling it as a “disgusting, rat and rodent infested mess." Protesters gathered outside the Marriott hotel on the Baltimore waterfront with a giant inflatable rat adorned with yellow hair and a red tie in tow. Demonstrators held signs that read “Welcome rat king” and “Trump and the GOP are the real rats.”

An giant inflatable rat depicting President Donald Trump is seen on the street near the U.S. House Republican Member Retreat, Thursday, Sept. 12, 2019, in Baltimore. (AP Photo/Nick Wass)

Inside the hotel, the president spoke to a friendly audience of legislators whose political futures are closely tied to how well he performs in next year’s election. They greeted Trump with a chant of "four more years" and gave him a standing ovation when he promised to uphold the right to keep and bear arms.

President Trump on Thursday made his first visit to Baltimore since insulting the city nearly two months ago, calling it as a “disgusting, rat and rodent infested mess,” where he addressed congressional Republicans, touted his administration’s accomplishments and even announced plans for a “substantial” tax cut for middle-income Americans. (FOX News)

Trump also referenced the Democratic presidential debate that was taking place at the same time as his speech as he talked about unemployment rates for African-Americans, which he claimed were “the lowest ever recorded."

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“I wonder if that would be mentioned tonight during the debate?” Trump asked. “I don’t think so.”

During his speech, Trump said, “The agenda of the Democrat party is the demolition of the American middle class.” He emphasized some of the biggest wins of his presidency, such as boosting military spending, slashing regulations and expanding a program that gives veterans the option to see private doctors outside the Veterans Affairs medical system.

President Donald Trump arrives in Baltimore, Thursday, Sept. 12, 2019, en route to joint fundraising committee reception, and the 2019 House Republican Conference Member Retreat Dinner. (AP/ Carolyn Kaster)

“We have done tremendous changes in our country and we are going to do a lot of other great changes,” Trump said, adding that additional time is needed “to hang on to what we have done” and that it would be a “disaster” if they don’t get the chance. He also stressed that it was important for the party to “stick together.”

“You have to fight like hell,” Trump told his legislative audience, adding that “our country will go to hell if any of these people [Democrats] get in.”

Trump obliquely addressed his earlier insults against Baltimore, promising Republicans would "fight for the future of cities like Baltimore that have been destroyed by decades of failed and corrupt rule."

Baltimore, a once-gilded American seaport, has undeniable drug and violent crime challenges. The city saw more than 300 homicides in 2018 for the fourth year in a row. It also contends with deep-rooted poverty and swaths of the city are populated with vacant, boarded-up homes.

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In July, the president was locked in a feud with Rep. Elijah Cummings, who represents the city's majority-black 7th Congressional District.

After Cummings criticized Border Patrol officials during a House Oversight Committee hearing in July, Trump claimed that conditions in Baltimore were “more dangerous” than those at the border, and said that “no human being would ever want to live there.” Democrats immediately rallied to Cummings’ side, some of them accusing Trump of being racist.

The GOP retreat was scheduled to be held in Baltimore before Trump got into his dispute with Cummings. On Thursday, the president said crushing regulations, crippling taxes and "unrestricted migration" have undermined law enforcement and devastated America's inner cities. "We're going to have to step up and doing something about it because we can't allow that to happen to our great cities," he said.

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Trump has not backed away from his charges that Democratic leaders are responsible for the ills of America’s biggest cities. On Thursday night the president also brought up San Francisco and Los Angeles, saying “we have to step in and do something” to address the homeless crisis there.

“We can’t allow that to happen, where major companies are leaving our cities, leaving our country, when they see that,” Trump said.

He added, “They are our great American cities and they are an embarrassment.”

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The White House said the president did not have any plans to explore Baltimore beyond his speech.

Fox News’ Brooke Singman and The Associated Press contributed to this report.