PHILADELPHIA — President Donald Trump called on fellow Republicans to help him enact “great and lasting change” during a party retreat Thursday, but offered the lawmakers few details about his views on key issues including tax reform and health care.

The president was greeted by cheers as he took the stage in a hotel ballroom, telling senators and House members, “This Congress is going to be the busiest Congress in decades — maybe ever.”

Trump’s election put Republicans in control of both the White House and Congress for the first time in more than a decade. Yet Trump’s often fluid ideology has sometimes put him at odds with his own party, making agreement on issues including a tax overhaul and entitlements no guarantee.

The president spoke about his agenda in broad terms and then skipped a planned question-and-answer session. He gave Republicans no specific marching orders for tackling the repeal and replace of “Obamacare,” one of the most complicated issues Congress is expected to tackle this year.

Trump said he had suggested to GOP leaders that they could “just do nothing for two years” in order to let Obamacare self-destruct and ramp up pressure on Democrats to join overhaul efforts.

“Except we have one problem — we have to take care of the American people,” he said.

President Donald Trump spoke Thursday at an annual GOP policy retreat in Philadelphia. Video by PBS NewsHour

Trump’s brief trip to Philadelphia marked his first flight on Air Force One, the familiar blue and white government plane that has long ferried presidents around the country and the world. Spokesman Sean Spicer described Trump — who traveled throughout the campaign and the transition on his own private jet — as being “in awe” of the presidential aircraft.

Trump saluted as he walked off his Marine helicopter and chatted with an Air Force officer who escorted him to the steps of the plane. He climbed the steps slowly but did not turn around and wave as presidents often do.

Trump’s midday remarks in Philadelphia came after several days of executive actions on trade and immigration. On Wednesday, he began overhauling the nation’s immigration rules and moved to jumpstart construction of his promised U.S.-Mexico border wall. He also ordered cuts in federal grants for “sanctuary cities,” which shield some immigrants from federal law enforcement, and authorized increases in the number of border patrol agents and immigration officers.

The moves on immigration caused immediate friction with Mexico, prompting President Enrique Pena Nieto to cancel a trip to Washington next week for his first meeting with the new president. It was a remarkable move by an ally and neighbor.

During his remarks to lawmakers, Trump cast the cancellation as a mutual decision. He said he and Pena Nieto “have agreed to cancel our planned meeting.” Trump had tweeted earlier Thursday that “it would be better to cancel the upcoming meeting” given Pena Nieto’s unwillingness to pay for the border wall.

Trump insists Mexico will pay, while Pena Nieto insists his country will not.

After returning to the White House, Trump planned to sign an executive action commissioning a probe of widespread voter fraud, Spicer said. Additional actions are planned for Friday, too, but Spicer said decisions were still to be made on exactly what Trump would sign.

The president is also expected to take steps, possibly as soon as this week, to restrict the flow of refugees into the United States. And he is considering plans to negotiate individual trade deals with the countries that have signed onto the proposed Trans-Pacific Partnership trade pact. Trump took steps earlier in the week to withdraw the U.S. from TPP, which he said puts American workers at a disadvantage.

The White House had said Trump would also meet Thursday afternoon with Sen. Orrin Hatch, R-Utah, and Rep. Kevin Brady, R-Texas. The meeting with Hatch, who is chairman of the Senate Finance Committee, and Brady, chairman of the tax-writing House Ways and Means Committee, has been rescheduled, the White House said.

The 12 executive actions Trump has signed (so far)