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.