"The Arizona National Guard will deploy 225 members of the Guard today to support border security measures," the state militia said in a statement.

Governor Doug Ducey said on Twitter that "additional members" would be deployed on Tuesday, without providing details.

"The Guard will provide air support, reconnaissance support, operational support, construction of border infrastructure and logistical support," the Arizona National Guard statement said.

The deployment came after Texas National Guard commander Brigadier General Tracy Norris announced on Friday that she was moving 250 troops to the state's own border with Mexico within 72 hours, "with supporting aircraft, vehicles and equipment."

Secretary of Defense Jim Mattis last week signed an order for "up to 4,000 National Guard personnel" to support the Department of Homeland Security's southern border security mission through to the end of September, the Defense Department said.

The department said the troops would not carry out law enforcement activities without the defense secretary's approval and would be armed only in "circumstances that might require self-defense."

Trump had said on Thursday that the final deployment would range from 2,000 to 4,000 troops, and he would "probably" keep many personnel on the border until his promised border wall is built.

The move has heightened tensions with Mexico, whose President Enrique Pena Nieto said Trump's "threatening or disrespectful attitudes" were unjustified.

If 4,000 troops were deployed, that would be about double the current US military presence in Syria and about half as many as the number of US troops in Iraq.

The National Guard has previously been deployed to help patrol the southern border, including in 2010 under former president Barack Obama, and from 2006-2008 under George W. Bush. Both deployments were limited to around a year.