When President Obama got on the telephone with President Dmitri A. Medvedev of Russia last month, he was under the impression that they were finally close to wrapping up a long-delayed arms control treaty that he had originally expected to sign in December.

But to Mr. Obama’s surprise, Mr. Medvedev was not ready to sign off on a deal and raised issues that required more discussion, American officials said. As he hung up, the officials said, a frustrated Mr. Obama realized that the two sides were not as close as he had thought and sent negotiators back to the table.

The fitful effort to fashion a treaty that would be a signature achievement of his presidency has demonstrated the hurdles Mr. Obama faces in his drive to reset relations with Russia after years of tension.

Diplomacy and energy are never far apart in the Persian Gulf. So, as American officials seek new international sanctions against Iran this week, it’s probably wise for them to remember how much the world’s global energy map has changed over the past decade.

Iran’s leaders certainly do, and they’ve been counting on their increased ties with Asian countries, especially China, as their trump card against efforts to hem in their nuclear program.

At the same time, the Iranians may want to reconsider just how much that trump card is worth. A number of experts say it is losing its value with each month that the stalemate over its nuclear program continues.

While there is a broad consensus about the relative decline of the US as a superpower, political commentators have debated about emerging political rivalries. A study of recent events, however, shows that instead of a straightforward bipolar or multipolar relationship, simultaneous cooperation and competition will be the likely template of relationships among the major powers - United States, China, the European Union, Russia, India and Brazil. The new pattern of fluid and ever-changing relationships between such powers will underscore the end of the uncontested global supremacy in economics, politics, military and culture that the US has enjoyed since 1991.

Attempts by each of the players to obtain the best economic and political advantage for themselves while cooperating on issues of common concern is likely to produce tension as well as unexpected accommodation and temporary alliances. The sharpest example of engagement and containment is the relationship between Beijing and Washington.

The United States is circulating a draft of new, tougher sanctions against Iran that concentrate on the banking, shipping and insurance sectors of Iran’s economy and is now waiting for China and Russia to signal that they are willing to start negotiating over the measures, United Nations Security Council diplomats said Wednesday.

The proposed sanctions would both broaden the scope and intensify three previous rounds of sanctions enacted since 2006 in an effort to persuade Iran to halt uranium enrichment and negotiate the future of its nuclear development program.

Russia is to buy four warships from France in the biggest defence deal with a Nato member since the end of the Cold War. In a move that has alarmed Georgia and the Baltic States, France and Russia said that they were in “exclusive talks” on the sale of Mistral-class amphibious assault ships.

President Sarkozy said that he wanted to “turn the page on the Cold War” after meeting President Medvedev in Paris.

Every four years the White House issues a “nuclear posture review.” That may sound like an anachronism. It isn’t. In a world where the United States and Russia still have more than 20,000 nuclear weapons — and Iran, North Korea and others have seemingly unquenchable nuclear appetites — what the United States says about its arsenal matters enormously.

President Obama’s review was due to Congress in December. That has been delayed, in part because of administration infighting. The president needs to get this right. It is his chance to finally jettison cold war doctrine and bolster America’s credibility as it presses to rein in Iran, North Korea and other proliferators.

Secretary of State Hillary Rodham Clinton called Monday for closer cooperation between Russia and NATO, the trans-Atlantic alliance that Moscow views with suspicion as a relic of the Cold War and a potential threat to its security.

In a speech launching an international seminar on revising NATO's mission for the 21st century, Clinton rejected Russian calls for a new European security treaty that Washington believes would lead to a diluting of NATO's influence in Europe and beyond.

Vice President Joseph Biden will begin the first push for congressional ratification of the United Nations nuclear test-ban treaty since the Clinton presidency, with a speech Thursday saying the Obama administration's large funding request for monitoring will make tests obsolete.

The speech at the National Defense University here will challenge liberal arms-control advocates to embrace a $624 million increase in nuclear-weapons funding, most of which would go to nuclear-weapons scientists to monitor the nation's aging stockpile without testing.

Russia raised Western hopes that it will support tougher international sanctions against Iran’s nuclear programme by announcing a delay in delivery of S-300 advanced air defence missiles.

The postponement for unspecified “technical problems” was made public a day after Binyamin Netanyahu, Israel’s Prime Minister, urged Russia to support “crippling” sanctions against Tehran during a visit to Moscow.

The United States and Israel have been pressing Russia not to deliver the S-300 missiles, which would make a successful military strike much more difficult if diplomacy failed to resolve the stand-off over Iran’s nuclear facilities.

A recent report by George Robertson, a former secretary general of NATO, and two co-authors, Franklin Miller and Kori Schake, criticizes the German proposal to withdraw the remaining American nuclear weapons from German territory as damaging not only to Germany, but to the alliance as a whole.

The authors argue that the proposal was driven more by populist sentiment than any long-term strategic goal. This observation is wrong and misleading. While the Robertson report is based on outdated perceptions, the arguments presented merit a substantive response.