Rights activists have described her detention and prosecution as part of an official effort to silence critics.
The U.S. State Department said the United States is "disturbed' by how Niyazova's trial was carried out and added that the charges were "politically motivated."
A court sentenced Niyazova on May 2, after she was found guilty of possessing anti-constitutional materials. Niyazova had also been found guilty of illegally crossing the country's border and fostering unrest with the help of foreign funding.
Human Rights Watch (HRW) has also called Niyazova's case "politically motivated," contending it is linked to articles she wrote about the killing of protesters by security forces in the Uzbek town of Andijon in May 2005.
The 32-year-old freelance journalist was reportedly collecting information about the Andijon violence in neighboring Kyrgyzstan before her detention.
Officials claim that fewer than 200 people -- most of them insurgents or security forces -- were killed in Andijon, while rights groups and eyewitnesses say several times that number of people died, most of them unarmed demonstrators that included many women.
Uzbek authorities' rejection of international calls for an independent probe into the circumstances of the bloodshed led to EU-led sanctions and friction between a number of Western governments and Tashkent.
HRW recently noted that "14 other human rights defenders" are also in Uzbek prisons for their criticism of official actions.
(Reuters, RFE/RL's Uzbek Service)