Ali Bibi, a liaison officer with the U.N. refugee agency, said the increased number of Syrian refugee arrival was due to the "security situation in southern areas bordering Jordan."
Two officers with the rebel Free Syrian Army coordinating the movement of refugees between Syria and Jordan said there were additionally thousands of refugees waiting to cross into Jordan.
They said the refugees moved recently from areas in the suburbs of the Syrian capital Damascus into two villages in Syria's south, namely Tal Shahab and Zeizoon, near the Jordanian frontier.
"They are anxious about a potential U.S. strike on Syria and are now just across the border waiting to see how things will develop," said one of the officers, estimating their number at nearly 40,000.
"They were given shelter, but they don't have enough food and water," he said.
Both officers spoke by telephone from Syria's southern region. They insisted on anonymity and declined to have their location identified for fear of reprisal by the Damascus government.
Jordan is the second largest host of Syrian refugees after Turkey, sheltering more than 560,000.