Image copyright AP Image caption Mr Abbott, seen speaking earlier in April, issued the directive on 28 April

Texas Governor Greg Abbott is coming under increasing criticism for ordering the Texas State Guard to monitor federal military exercises.

The exercises drew concerns that the government could implement martial law or confiscate citizens' guns.

Former Texas Governor Rick Perry, the Pentagon, and the White House have suggested the concerns and Mr Abbott's request were unfounded.

The exercises, called Jade Helm 15, are set to begin in July.

"In no way will the constitutional rights or civil liberties of any American citizen be infringed upon while this exercise is being conducted," White House Press Secretary Josh Earnest said. "I have no idea what [Abbott] is thinking."

Texas and six other states are hosting the war simulations, which will last three months, and take place on public and private land. The Army said that the topography and terrain of the selected areas are ideal for training, because they mimic foreign combat zones.

"It's OK to question your government. I do it on a regular basis. But the military is something else," Mr Perry told the Dallas Morning News on Tuesday. "Our military is quite trustworthy. The civilian leadership, you can always question that, but not the men and women in uniform."

Image copyright Reuters Image caption Former Governor Perry, seen here speaking earlier in April, said the US military is trustworthy

Mr Abbott's request, written in a directive dated 28 April, came the day after a US Army commander answered questions from a crowd of 200 people in a rural part of Texas.

"In the case of private land, we've spoken and made detailed coordination with the patriotic Americans who have volunteered their land for the use of this important training," Pentagon Spokesman Army Col Steve Warren said, according to McClatchy DC.

Over two hours, US Army Lt Col Mark Lastoria told the crowd that the operation would involve 1,200 soldiers from all four branches of the military.

Analysis: Gary O'Donoghue, BBC News, Washington

For the 26 million people who call Texas home, one thing above all unites: Their state is not to be messed with.

Suspicion about the federal government is to be found everywhere in the United States, but in Texas the level of mistrust is deep and enduring.

So the idea that the military might be planning a takeover, or the introduction of martial law, has found plenty of followers.

What's surprising is that the Governor seems to agree with them.

But what none of them seems to realise is that Texas is home to one of the biggest permanent populations of military personnel in the country.

Take Fort Hood near Waco. Almost 45,000 active service members call the fort home.

Mr Lastoria said that people with a "personal agenda" about the exercises had been spreading false information.

Suspicions were stoked when some conservative websites published a map that labelled Texas, Utah and parts of California as "hostile" territory.

The US Army has acknowledged that the scale and scope of Jade Helm made these - otherwise routine - training exercises unique.