WASHINGTON —  Philadelphia will get some time in the international spotlight this week, as President Trump makes the city what is likely to be his first major stop outside Washington since his inauguration.

The president is scheduled to address congressional Republicans, who will be gathering at the Loews hotel Wednesday through Friday as they try to map out an aggressive agenda for their newfound power in Washington. Trump won't be the only world leader in the city: British Prime Minister Theresa May is also expected to speak at the retreat.

Organizers have not released details regarding where and when Trump will speak, but in past congressional retreats such keynote speeches were typically not open to the public. Trump's spokesman, Sean Spicer, said the president would travel to Philadelphia on Thursday.

The gathering will give the new president a chance to lay out his top legislative priorities to the full GOP contingent from the House and Senate. The event is also expected to draw protesters hoping to build on the momentum of the women's marches across the country Saturday.

City officials said they would announce on Tuesday any expected street closings or other measures from by the event.

Trump's address will come as he launches into his first term — typically a time when presidents try to tackle some of their top priorities — and Republicans try to determine how to use their control of the White House and both chambers of Congress.

Republicans have united around a repeal of the Affordable Care Act, but there is still significant debate over how quickly to move and what a replacement plan should look like. An overhaul of the federal tax code follows close behind on the GOP wish list, though that would also be a complex undertaking with many details to work out.

"We're looking for a place where we can sit down and talk to our House colleagues about some of the big policy decisions we're going to have to make, health care being one of them, working with the new administration, and certainly tax reform," said Sen. John Cornyn of Texas, the Senate's second-ranking Republican.

U.S. Rep. Pat Meehan of Delaware County said the annual retreat gives lawmakers from opposite sides of the Capitol a chance to exchange ideas, get to know one another, and try to find unity in their legislative plans.

"It also allows more vetting of different opinions," he said.

Republicans generally agree on their big picture goals, said Sen. Pat Toomey (R., Pa.), but the retreat gives them a chance to refine the details. Toomey, for example, said he would give a presentation, along with two of the Senate's top Republicans, analyzing tax reform plans. A tax code overhaul, he said, has "a good chance" to get done this year and "would be very, very helpful for our economy."

This year's retreat includes even more weight for Republicans: For the first time since the Bush administration they have control of the presidency and both chambers of Congress, giving them a real chance to advance major policy changes after years of gridlock.

"There is ... a sense of optimism about the chance to see matters from original drafting to potentially being signed by the president. It also is, I hope, met with equal measures of realism about the challenges and the dynamics of working with Democrats in the Senate and what can be accomplished," Meehan said.

Exactly how Republicans plan to use that opening is unclear. Even some Republican lawmakers have complained that they don't know what to expect from Trump, who has offered few details on his policy vision and has at times contradicted his own statements, or been contradicted by his cabinet nominees.

"It's certainly going to be helpful for the president to continue to flesh out his priorities," Toomey said.

Meehan said he hoped the event includes a chance for lawmakers to ask questions of the president. He also speculated that May could address the looming United Kingdom exit from the European Union, a move that could have a significant impact on the close U.S. ally.

He noted that previous retreats have also drawn top international names, including former British Prime Minister Tony Blair, though Blair was not in office at the time he visited.

Liberal groups, meanwhile, are planning their own response.

"The Republicans and Trump have chosen the City of Brotherly Love to try to dismantle everything this country cares about — our health care, our civil liberties, our education system. We're coming together to say no — not in our city," said a statement from Derrick Mathis, a member of the 215 People's Alliance, one of the protest organizers.

The scheduled events include a march and rally Thursday at Thomas Paine Plaza, and plans for a rally outside the hotel that afternoon, starting at 4 p.m.

City officials are still awaiting details of Trump's plans, but one, speaking on the condition of anonymity, said the president would not stay overnight. "He is coming and leaving," the official said.

The U.S. Secret Service is still coordinating with Philadelphia police to finalize security plans, and it is too early to tell whether Trump's visit will warrant more manpower than past presidential stopovers in the city, said James Henry, special agent in charge of the Philadelphia Field Office.

"Based on what we saw from the inauguration and the days following that with the number of protests, that's something that's taken into consideration," he said. "We plan to protect the president of the United States, but the Secret Service respects people's rights to exercise their First Amendment rights."

Some intermittent street closures are likely to accommodate the presidential motorcade, Henry said.​

Follow Jonathan Tamari on Twitter or email him at jtamari@phillynews.com.