Washington (CNN) Jared Kushner has been unable to obtain a full security clearance in part because of special counsel Robert Mueller's investigation, according to two sources familiar with the matter.

Kushner, President Donald Trump's son-in-law and senior adviser, is unlikely to obtain the full clearance as long as the special counsel's probe is ongoing, one of the sources said.

Kushner's application for a top-level security clearance has been held up for over a year in part because it cannot be completed while the special counsel's team continues to probe Kushner's contacts with Russians and his financial dealings with foreigners, the sources said. During that time, Kushner has been able to access the government's most sensitive secrets thanks to an interim security clearance. But that access could soon be cut off -- unless Trump steps in with a waiver.

There is no indication that Mueller is close to wrapping up his investigation, and an impending crackdown by White House chief of staff John Kelly aimed at restricting access to classified information for those with long-pending interim clearances is expected to nix or downgrade Kushner's interim security clearance. The combination of factors could leave Kushner without a security clearance for months to come, even as he tackles sensitive issues like the Israeli-Palestinian conflict and the United States' relationship with Mexico.

The situation is especially complicated for Kushner because the FBI isn't sharing information with the White House that would typically be relevant in a background investigation for security clearance. That's because sharing such information could compromise the special counsel's probe.

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