Jeff Fortenberry, (R-NE) speaks during testimony by then US Secretary of State Mike Pompeo at a hearing on the State Department's budget request for 2020 in Washington, US March 27, 2019. [Photo/Agencies]

US Congressman Jeff Fortenberry announced on Saturday that he will resign from office, two days after being convicted of three felonies.

Fortenberry, a Nebraska Republican who has served in Congress since 2005, said that his last day as a federal legislator will be March 31, according to a letter he sent to his House colleagues.

"Due to the difficulties of my current circumstances, I can no longer effectively serve," he wrote.

Fortenberry, 61, was found guilty on Thursday of one count of scheming to falsify and conceal material facts and two counts of making false statements to federal investigators.

The conviction arose from a federal investigation into "illegal contributions made by a foreign national" to Fortenberry's 2016 re-election campaign.

A sentencing hearing was scheduled for June 28. Each of the three felony charges carries a statutory maximum penalty of five years in federal prison.

A special election will be held no later than 90 days after Fortenberry's seat becomes vacant, according to rules.

The US federal law prohibits contributions made directly or indirectly by or from foreign nationals in connection with any federal, state, or local election.