WASHINGTON (Reuters) - Defense Secretary Robert Gates said on Tuesday he was satisfied with the pace of U.S. planning to counter the threat posed by Iran’s nuclear program, brushing aside Republican charges of a strategic vacuum.

Pentagon war planners are drawing up military options should President Barack Obama decide to use force against Iran, even though Gates and other U.S. military leaders have made clear that it would be the option of last resort should sanctions and diplomacy fail.

Gates’s comments, at a joint news conference with visiting Israeli Defense Minister Ehud Barak, appeared aimed at reassuring U.S. lawmakers and overseas allies that the Obama administration is moving swiftly to craft a workable strategy.

“I’m very satisfied with the planning process, both within this building and in the inter-agency. We spend a lot of time on Iran and we’ll continue to do so,” Gates said at the Pentagon, the headquarters of the U.S. military.

Republicans and some Democrats in Congress have complained that it is unclear how far the Obama administration would be willing to go to stop Iran from getting a nuclear bomb.

The United States and other Western powers assert that Iran’s nuclear program is aimed at making weapons, but Tehran says it is for peaceful purposes.

Gates on April 18 said he had sent a secret memorandum to the White House in January identifying “next steps” in the U.S. planning process to curb Iran’s nuclear program, but denied the memo represented a “wake up call” that the United States lacks an effective strategy toward Iranian atomic ambitions.

Barak on Tuesday voiced satisfaction, at least for now, with the U.S. focus on curbing Iran’s nuclear program using diplomatic and economic sanctions rather than military force.

“The time is clearly at this stage ... for sanctions and diplomacy,” Barak told reporters with Gates at his side.

‘LIMITED IN TIME’

But underlining Israeli concerns that the United States may drag out the process, Barak said Israel expected any new U.N. and bilateral sanctions imposed on Iran to be “effective and to be limited in time so we will be able to judge to whether, what kind of results, stem from the sanctions regime.”

While directing the Pentagon to have military options ready should Obama call for them, Admiral Mike Mullen, chairman of the U.S. military’s Joint Chiefs of Staff, has said policymakers face difficult choices in trying to keep Iran from getting a nuclear bomb without setting off a broader conflict.

While the military options available to Obama would go “a long way” to delaying Iran’s nuclear progress, they may not set the country back long-term, Mullen recently told an audience at Columbia University in New York.

Michele Flournoy, U.S. under secretary of defense for policy, said on April 21 military force was “an option of last resort,” and added: “It is not on the table in the near term.”

Senator John McCain, a leading Republican who lost to Obama in the 2008 U.S. presidential election, has called the U.S. mixed messages a sign that “we do not have a coherent policy.”

U.S. Secretary of State Hillary Clinton, who met Barak earlier on Tuesday, said Washington was seeking tough new sanctions to “sharpen the choices that Iran’s leaders face.”

Over the weekend, Iran’s foreign minister and the director general of the U.N. International Atomic Energy Agency met in Vienna but made no progress in advancing a months-old plan for Iran to ship some of its low-enriched uranium out of the country to be turned into fuel for a medical research reactor.

“So far as we are aware based on the readout of the meeting between the Iranian foreign minister and the director general of the IAEA, there was nothing new that was presented,” Clinton told reporters during a meeting with a visiting European Union official.

“Iran’s continued disregard for its international obligations underscores the importance of united international pressure to change its policies,” Clinton added. “The United States is working with our partners ... on tough new sanctions that will further sharpen the choices that Iran’s leaders face.”