For a man with a bad back, Russian President Vladimir Putin sat up straight for more than four hours Thursday in his annual marathon news conference, brushing off claims that he's an authoritarian leader and lashing out at the U.S.

The annual news conferences have become a grueling and elaborate piece of theater, a show both of Putin's vigor and of his domination of Russian politics.

The top story on Russian news channels before the news conference itself was assiduously detailed reporting on preparations for the event, including speculation on whether he would set a new record for length.

He didn't. This year's clocked in at 4:33, seven minutes short of the record set in 2008. But at age 60, Putin is still vigorous and he showed no sign of the back injury that forced him to put off some foreign trips this fall.

During the news conference, Putin lashed out at the United States, complaining that a recent U.S. law that allows sanctions on Russians deemed to be human rights violators was arrogant.

"Why does one country consider itself entitled to spread its jurisdiction to the entire world?" he said in his characteristic rapid-fire delivery.

The U.S. law sparked a retaliatory measure now being considered by the lower house of parliament, which includes a ban on Americans adopting Russian children. Putin said the harsh proposal was an "appropriate" reaction to the U.S. law, but was noncommittal on whether he would sign it. Some top government officials have openly opposed the move.

Putin also rejected the frequent description of his rule as authoritarian, saying that he wouldn't have stepped down after two terms if that were the case.

"If I had thought that a totalitarian or an authoritarian system is the preferred one, I would have just changed the Constitution," he said. "It would have been easy to do. It does not even require a popular vote."

The Russian leader returned to the presidency in May after stepping aside due to term limits for a four-year hiatus as prime minister, during which he remained Russia's dominant figure and overshadowed placeholder President Dmitry Medvedev.

Notably, Putin used the news conference to assert that Russia recognizes change is needed in Syria. The admission does not appear to herald a change in Russia's stance _ Putin reiterated Moscow's long-standing call for negotiations to end the fighting between Bashar Assad's regime and opposition forces _ but may show a growing willingness to view its longtime ally as obsolete.