Can the right of priority be restored if the U.S. application is filed late?

Yes, the right of priority can be restored if the U.S. application is filed after the 12-month priority period (or 6-month period for design applications), but within 2 months of the expiration of the priority period, if the delay was unintentional.

37 CFR 1.55(c) states: “If the subsequent application has a filing date which is after the expiration of the period set forth in paragraph (b)(1) of this section, but within two months from the expiration of the period set forth in paragraph (b)(1) of this section, the right of priority in the subsequent application may be restored under PCT Rule 26bis.3 for an international application, or upon petition pursuant to this paragraph, if the delay in filing the subsequent application within the period set forth in paragraph (b)(1) of this section was unintentional.”

To restore the right of priority, the applicant must file a petition including:
1. The priority claim
2. The petition fee
3. A statement that the delay was unintentional

The USPTO may require additional information to determine if the delay was truly unintentional.