By Jon Herskovitz

AUSTIN, Texas (Reuters) - A federal judge on Thursday dealt another blow to Texas' bid to halt the resettlement of Syrian refugees in the state, saying it did not have the authority to set immigration policy and had failed to show that a private relief effort was unlawful.

Texas has lost a series of court decisions since filing a federal lawsuit in December in response to the International Rescue Committee's plan to resettle six refugees fleeing Syria's civil war.

U.S. District Judge David Godbey ruled on Thursday that the federal government, not individual states, had the power to set immigration policy, and found that Texas brought no plausible argument to back its claims that the relief agency was acting illegally in bringing the refugees into the state.

"This ruling is a strong rebuke of unconstitutional efforts to block refugee resettlement," said Cecillia Wang, director of the American Civil Liberties Union’s Immigrants' Rights Project and the IRC's lead counsel.

Texas Attorney General Ken Paxton said in a statement: "I am disappointed with the court's determination that Texas cannot hold the federal government accountable to consult with us before resettling refugees here."

The Obama administration has pledged to take in 10,000 people fleeing the conflict in Syria. Resistance to that policy initially was generally muted, but gained momentum after the Islamic State's attacks on Paris in November.

Republican Texas Governor Greg Abbott was one of the first of more than 30 U.S. governors, mostly Republicans, seeking to block the resettlement on the basis of security worries.

Abbott has expressed concerns that U.S. security screening is ineffective and could allow people with ties to terrorism to be admitted.

The Texas Health and Human Services Commission had argued that the federal government and the relief agency violated their statutory duty under a law called the U.S. Refugee Act to consult with the state in advance of placing refugees in Texas.

"The court previously determined that the Refugee Act does not confer a private right of action for the states to enforce its provisions," Godbey wrote.

Since fiscal year 2011, 243 Syrian refugees have been resettled in Texas, a U.S. court filing in December showed, making the state one of the main U.S. relocation sites since the Syrian civil war erupted five years ago.

(Reporting by Jon Herskovitz; Additional reporting by Lisa Maria Garza in Dallas; Editing by Will Dunham and Paul Simao)