International election monitors have been threatened with prosecution in Texas if they observe voting in the state a little too closely on November 6.
Legal officials in the state have warned that monitors would not be allowed to enter polling stations.
The exchange pitted the Vienna-based human rights watchdog Organisation for Security and Co-operation in Europe against Texas Attorney General Greg Abbott, who warned the OSCE not to interfere with polling in state elections.
"The threat of criminal sanctions against OSCE/ODIHR [Office for Democratic Institutions and Human Rights] observers is unacceptable," Janez Lenarcic, director of the ODIHR monitoring arm, said in a statement.
"The United States, like all countries in the OSCE, has an obligation to invite ODIHR observers to observe its elections."
Abbott told the Reuters news agency on Wednesday that he was considering legal action against the group if it does not concede that it will follow the state's laws.
"They act like they may not be subject to Texas law and our goal all along is to make clear to them that, when they're in Texas, they're subject to Texas law, and we're not giving them an exemption," he said.
Abbott is sceptical about why the group wants to look at elections in Texas.
'Suppressing voter integrity'
"Our concern is that this isn't some benign observation but something intended to be far more prying and maybe even an attempt to suppress voter integrity," he said.
In a letter on Tuesday to the Warsaw-based ODIHR, Abbott had noted that the group's representatives were not authorised by Texas law.
"No UN monitors/inspectors will be part of any TX election process; I commend @TXsecofstate for swift action to clarify issue."
- Tweet by Texas Governor Rick Perry
"It may be a criminal offence for OSCE's representatives to maintain a presence within 100 feet (30 metres) of a polling place's entrance. Failure to comply with these requirements could subject the OSCE's representatives to criminal prosecution for violating state law," he added.
He cited reports that monitors had met with organisations challenging voter identification laws. Texas' voter ID law was blocked earlier this year by a federal court, and Abbott has said he will appeal to the US Supreme Court.
"The OSCE may be entitled to its opinions about voter ID laws, but your opinion is legally irrelevant in the United States, where the Supreme Court has already determined that voter ID laws are constitutional," Abbott wrote.
Texas Secretary of State Hope Andrade also wrote to the United Nations-affiliated OSCE/ODIHR on Tuesday, saying that it was key for Texans to understand that the organisation has no jurisdiction in the state.
Republican Texas Governor Rick Perry tweeted on Tuesday: "No UN monitors/inspectors will be part of any TX election process; I commend @TXsecofstate for swift action to clarify issue."
The 56-member OSCE routinely sends monitors to elections, and noted November's elections would be the sixth US vote that ODIHR had observed "without incident" since 2002.
For next month's elections, it has a core team of 13 experts from ten OSCE countries based in Washington, and 44 long-term observers deployed across the country.
The monitoring group has reportedly shared its "grave concern" about the threat of Texas prosecutions with US Secretary of State Hillary Clinton.
"Our observers are required to remain strictly impartial and not to intervene in the voting process in any way," Lenarcic said. "They are in the United States to observe these elections, not to interfere in them."