"The president felt it was necessary," said State Department spokesman Robert Wood, referring to the renewal of the sanctions, which is required each year by Congress.
"This shows you that we still have some very serious concerns about Syrian behavior and activities in the world."
The sanctions, imposed by former President George W. Bush, prohibit arms exports to Syria, block Syrian airlines from operating in the United States and deny Syrians suspected of being associated with terrorist groups access to the US financial system.
While the United States has made clear it wants better ties with Syria, which appears on the US list of state sponsors of terrorism, the renewal of the sanctions shows it is not yet ready for a dramatic improvement.
"We need to see concrete steps from the Syrian government to move in another direction," Wood told reporters.
President Barack Obama signed the executive order on Thursday extending the sanctions, shortly after two US envoys met Syrian Foreign Minister Walid al-Moualem in Damascus.
'There is a lot Syria needs to do'
The visit by senior State Department official Jeffrey Feltman and White House National Security Council official Daniel Shapiro was their second since Obama took office in January and started talking to Damascus.
The two officials told their Syrian counterparts the United States was committed to pursuing a peace deal between Syria and Israel, a main foreign policy objective for Damascus.
They also discussed Syria's role in Iraq, where Washington has accused Damascus of allowing fighters to cross into its neighbor, and Lebanon, where the United States accuses Syria of playing a destabilizing role.
"Part of Feltman's trip to the region was trying to get the Syrians to take some steps that will move us toward a better relationship. But there is a lot that Syria needs to do," said Wood.
The United States wants a commitment from Syria that it will not interfere with a June election in Lebanon, which US Secretary of State Hillary Clinton visited last month to show US support.
The administration hopes that direct talks with Syria, which will continue despite the sanctions, will weaken its ties to Iran.
Syria's President Bashar al-Assad indicated this week he did not plan to change course. After meeting Iranian President Mahmoud Ahmadinejad in Damascus, he said their strategic relationship contributed to Middle East stability.
The US ambassador was pulled out of Syria after the February 2005 assassination of former Lebanese Prime Minister Rafik al-Hariri. Syria denies any involvement in the killing but the United States pointed fingers at Damascus.