WASHINGTON — The Obama administration is accelerating the deployment of new defenses against possible Iranian missile attacks in the Persian Gulf, placing special ships off the Iranian coast and antimissile systems in at least four Arab countries, according to administration and military officials.

The deployments come at a critical turning point in President Obama’s dealings with Iran. After months of unsuccessful diplomatic outreach, the administration is trying to win broad international consensus for sanctions against the Iranian Revolutionary Guards Corps, which Western nations say control a covert nuclear arms program.

Mr. Obama spoke of the shift in his State of the Union address, warning of “consequences” if Iran continued to defy United Nations demands to stop manufacturing nuclear fuel. And Secretary of State Hillary Rodham Clinton publicly warned China on Friday that its opposition to sanctions was shortsighted.

The news that the United States is deploying antimissile defenses — including a rare public discussion of them by Gen. David H. Petraeus — appears to be part of a coordinated administration strategy to increase pressure on Iran.

The deployments are also partly intended to counter the impression that Iran is fast becoming the most powerful military force in the Middle East, to forestall any Iranian escalation of its confrontation with the West if new sanctions are imposed. In addition, the administration is trying to show Israel that there is no immediate need for military strikes against Iranian nuclear and missile facilities, according to administration officials who spoke on the condition of anonymity.

By highlighting the defensive nature of the buildup, the administration was hoping to avoid a sharp response from Tehran.

Military officials said that the countries that accepted the defense systems were Qatar, the United Arab Emirates, Bahrain and Kuwait. They said the Kuwaitis had agreed to take the defensive weapons to supplement older, less capable models it has had for years. Saudi Arabia and Israel have long had similar equipment of their own.

General Petraeus has declined to say who was taking the American equipment, probably because many countries in the gulf region are hesitant to be publicly identified as accepting American military aid and the troops that come with it. In fact, the names of countries where the antimissile systems are deployed are classified, but many of them are an open secret.

The general spoke about the deployments at a conference at the Institute for the Study of War here on Jan. 22, saying that “Iran is clearly seen as a very serious threat by those on the other side of the gulf front.”

General Petraeus said that the acceleration of defensive systems — which began when President George W. Bush was in office — included “eight Patriot missile batteries, two in each of four countries.” Patriot missiles are capable of shooting down short-range offensive missiles.

He also described a first line of defense: He said the United States was now keeping Aegis cruisers on patrol in the Persian Gulf at all times. Those cruisers are equipped with advanced radar and antimissile systems designed to intercept medium-range missiles. Those systems would not be useful against Iran’s long-range missile, the Shahab 3, but intelligence agencies believe that it will be years before Iran can solve the problems of placing a nuclear warhead atop that missile.

Iran contends that it is not trying to develop nuclear weapons, and that its program is for energy production. The White House declined to comment on the deployments.

But administration officials who spoke on the condition of anonymity said the moves have several aims. “Our first goal is to deter the Iranians,” said one senior administration official. “A second is to reassure the Arab states, so they don’t feel they have to go nuclear themselves. But there is certainly an element of calming the Israelis as well.”

As Iran’s nuclear program proceeds — more slowly, American intelligence officials say, than the United States had once thought — Israel has hinted at various times that it might take military action against the country’s military facilities unless it is convinced that Mr. Obama and Western allies are succeeding in stopping the program.

Mr. Obama’s national security adviser, Gen. James L. Jones, took an unannounced trip to Israel this month, partly to take the temperature of the Israeli government and to review both economic and covert programs now under way against the Iranian program, according to officials familiar with the meeting.

American officials argue that the willingness of Arab states to take the American emplacements, which usually come with a small deployment of American soldiers to operate, maintain and protect the equipment, illustrates the region’s growing unease about Iran’s ambitions and abilities.

Gulf countries are also taking steps of their own to harden their defenses. Saudi Arabia and the United Arab Emirates have bought more than $15 billion in American arms in the past two years, including missile defense systems. The United States is helping support a plan by Saudi Arabia to triple the size, to 30,000 people, of a Saudi force that protects the kingdom’s ports, oil facilities and water-desalinization plants, a senior military officer said. The Washington Post reported both steps on its Web site on Saturday.

One senior military officer said that General Petraeus had started talking openly about the Patriot deployments about a month ago, when it became increasingly clear that international efforts toward imposing sanctions against Iran faced hurdles, and the administration’s efforts to engage Iran were being rebuffed by the Tehran government. In October, the two countries reached an agreement in principle to move a significant portion of Iran’s nuclear fuel out of the country, but Iran backed away from the deal.

In discussing the Patriots and missile-shooting ships, General Petraeus’s main message has been to reassure allies in the gulf that the United States is committed to helping defend the region, said the military officer, who spoke on the condition of anonymity because of the delicate nature of the topic. But the general’s remarks were also a pointed reminder to the Iranians of American resolve, the officer said.