WASHINGTON (AFP) - The United States (US) is restricting the movement of Syria's United Nations (UN) ambassador, limiting him to a 40km radius around New York City, the State Department said on Wednesday.

Officials gave no explanation for the move against Mr Bashar Jaafari but US relations have deteriorated sharply with Damascus since Syrian President Bashar al-Assad led a crackdown against a pro-democracy uprising in 2011.

"We have delivered a diplomatic note to the permanent representative of the Syrian mission to the United Nations in New York informing him that he is restricted to a 25-mile (40 kilometer) travel radius," State Department spokesman Jen Psaki said.

The note was delivered at the end of February, she told reporters.

Some other countries' UN envoys face similar restrictions, she said. Envoys from Iran and North Korea are among them.

"So this is not something that is out of the realm of what we've done before," Ms Psaki said.

The Coalition for a Democratic Syria, an association of Syrian-American groups, welcomed the announcement, accusing the diplomat of trying to fuel sectarian divisions among Syrians in his public appearances in the US.

"This development has been a long-standing objective that the Syrian-American community has been trying to achieve for the past five months," said Mr Chad Brand, a spokesman for the coalition.

For the past six months, Mr Jaafari "has been conducting a series of propaganda tours across the United States to mislead Americans and sow sectarian discord among Syrian-Americans", he said.

The US has closed its embassy in Damascus but has not cut off diplomatic ties with Syria, despite repeated condemnation of the Assad regime.

The US ambassador to Syria, Mr Robert Ford, who had cultivated contacts with Syria's opposition, stepped down last week. Mr Ford left the Syrian capital in 2011, when the popular uprising against Mr Assad turned into a bloody civil war.