David Jackson and Jim Michaels

USA TODAY

WASHINGTON — President Obama said Thursday that he authorized "targeted airstrikes" if needed to protect U.S. personnel in Iraq, as well as airdrops of food and water to religious minorities in Iraq who are under siege from Islamic militants and trapped on a mountaintop.

"Today, America is coming to help," Obama said.

The president's announcement Thursday amounts to a significant escalation of involvement in the growing Iraqi crisis, but Obama attempted to assure the American public that it would not lead to U.S. involvement in a ground war there.

The administration has been weighing options for weeks, but the issue has come to a head with a mounting humanitarian crisis and unrelenting progress by Islamist extremists.

The most immediate crisis involved the Yazidis, a small religious minority, who have fled their homes and are trapped on a mountaintop surrounded by Islamist militants and are facing dehydration and starvation.

The U.S. military made an initial airdrop of meals and water to thousands of civilians threatened by militants on Thursday. The aircraft that made the drop safely exited the region after conducting a low-level flight and staying over the area for 15 minutes.

Three U.S. cargo aircraft delivered 72 bundles of supplies, including food and water, the Pentagon said. The aircraft were escorted by two FA-18 fighter attack jets.

The United States "cannot turn a blind eye" while innocent families face the prospect of "genocide," Obama said, justifying U.S. military action that could eventually include airstrikes.

Obama said U.S. aid would turn to airstrikes, which would represent a much deeper involvement in the conflict, in order to prevent militants from reaching Irbil, the capital of the Kurdish region. Irbil is home to a U.S. Consulate and a joint U.S.-Iraqi security base.

The airstrikes depend on whether U.S. personnel and facilities are directly threatened by the militants, Obama said.

Obama met with his national security team throughout the day, officials said, and aides have been briefing congressional leaders.

On Thursday, The New York Times reported, citing Kurdish sources, that airstrikes had started. Rear Adm. John Kirby, the spokesman for Defense Secretary Chuck Hagel, quickly denied those reports.

"Press reports that U.S. has conducted airstrikes in Iraq completely false. No such action taken," Kirby said in a statement on Twitter.

The plight of the Yazidis in recent days attracted world attention. They were forced to flee their homes when militants attacked Sinjar in northern Iraq. The militants consider the Yazidis as apostates.

Tens of thousands of refugees fled into the mountains, perhaps hoping to reach the Kurdish region in the north, but were trapped because of militant activity between the mountain and the Kurdish area, and are running short on food and water.

The militants, who belong to a group called the Islamic State, have had a string of recent successes in the north.

On Thursday militants attacked a string of Christian villages, worsening an already desperate humanitarian crisis and dealing a blow to the Kurdish forces defending the region.

Lawmakers from both parties expressed general support for Obama's new Iraq strategy.

Two Republican senators -- John McCain of Arizona and Lindsey Graham of South Carolina -- issued a joint statement saying that the plans Obama discussed are fine, but do not go far enough to meet the "expansionist" threat posed by the rebels known as ISIS.

"The President needs to devise a comprehensive strategy to degrade" the militant army, they said. "This should include the provision of military and other assistance to our Kurdish, Iraqi, and Syrian partners who are fighting ISIS."

Reports from the region also indicated that the militants may have seized Mosul Dam, a massive hydroelectric structure that would give the rebels control of resources and the ability to flood a wide swath of territory.

The Associated Press said the reports were based on residents who live near the dam who asked not to be named.

The militants were also fighting in an effort to seize the Haditha dam in the west. The two facilities would allow rebels to control water flowing south in the Tigris and Euphrates and much of the power supply for Baghdad.

The developments this week were particularly worrying because the militants dealt a blow to the Kurdish forces, called the peshmerga, which have a reputation of being disciplined and well-trained. The peshmerga were defending Sanjir and the Christian villages that were overrun by militants.

The militants have been pressing the pershmerga all along the border of the Kurdish region, making it hard for the Kurdish forces to concentrate their forces in order to effectively defend towns or to counterattack, said Jessica Lewis, a military analyst with the Institute for the Study of War.

The strategy appears to have worked for the militants. "This tells us (Islamic State) ... is a formidable force," Lewis said.