WASHINGTON (AP) — The U.S. said Tuesday the Thai military's declaration of martial law is allowed by the nation's constitution and its actions to date won't trigger sanctions.

Top American diplomat for East Asia, Daniel Russel, called for the early restitution of democracy and free and fair elections after the military intervened after months of violent political unrest.

But Human Rights Watch criticized the Obama administration for failing to call for the immediate reversal of martial law, saying that would be the quickest path to restore democracy.

The Thai army declared it was not launching a coup — something that has happened about a dozen times in modern Thai history. But it quickly imposed restrictions on news and social media, with 14 satellite TV channels from both anti-government and pro-government sides reportedly forced off the air.

Thailand is America's oldest ally in Asia and a close military partner, but under U.S. law, sanctions kick in if a country receiving American military aid suffers a coup. Following Thailand's last military coup in 2006, the U.S. froze military assistance for a year-and-a-half until democracy was restored.

State Department spokeswoman Jen Psaki said the military's actions so far have not triggered such a response. But she said the U.S. expects the Thai military to abide by its commitment that martial law is a temporary step to prevent violence and it will respect democratic institutions, including freedom of the press.

"As you may know, martial law, the declaration of that is allowed for in the Thai constitution. But we're certainly closely watching what's happening on the ground, and we'll continue to make evaluations of what's happening," Psaki told a regular press briefing.

Human Rights Watch said it was concerned the U.S. response amounted to de facto acceptance of the army seizing power from the civilian administration.

"Instead of making excuses for the Thai military, or offering misplaced legal justifications, the US should be calling for martial law to be ended," said John Sifton, the rights group's Asia advocacy director in Washington.

Thailand has been gripped by off-and-on political turmoil for the past eight years, that broadly speaking pits the mostly rural supporters of exiled former Prime Minister Thaksin Shinawatra and the conservative establishment in Bangkok. Some 28 people have been killed and more than 800 injured in the past six months of unrest.