WASHINGTON — Jared Kushner, the president’s son-in-law and senior adviser, has been stripped of his top-secret security clearance after months of delays in completing his background check, and will now be limited in his ability to view highly classified information, a White House official and another person familiar with Mr. Kushner’s situation said on Tuesday.

Mr. Kushner’s clearance was reduced to the level of secret and his official portfolio inside the West Wing, especially with regard to his globe-trotting foreign affairs work on behalf of President Trump, is expected to be sharply reduced, as well, the people said.

Since the beginning of the Trump administration, both Mr. Kushner, 37, and his wife, Ivanka Trump, the president’s elder daughter, 36, have enjoyed a special status within the White House as both family members and assistants to the president. But the complicated finances surrounding Mr. Kushner’s family’s vast real estate empire and his qualifications for the foreign policy responsibilities given to him by his father-in-law invited scrutiny from the start.

Often seen by Mr. Trump’s side during key moments of international diplomacy and presidential announcements during much of 2017, Mr. Kushner accompanied Mr. Trump on trips to Asia, including China and Japan; to the Mideast, including Israel and Saudi Arabia; and to Europe, meeting with officials in each place. He also made his own trips abroad.