The Pentagon said Thursday it would cancel a long-range radar that the Bush administration had planned to install in the Czech Republic and ground-based interceptors planned for Poland to protect Europe from Iran's long-range missiles. Instead, officials said, they would boost defenses against short- and medium-range missiles. Russia had long objected to plans for the missile installations on its doorstep, and Russian Prime Minister Vladimir V. Putin praised the shift Friday. The Obama administration clearly was betting that, despite having no public guarantees, Moscow would accept the overture and as a result would increase pressure on Iran. The White House gamble suggests that senior administration officials hope that, strains aside, the U.S. and Russia will agree they have a common interest in opposing Iran's missile development and halting its nuclear program. But Russia does not view Iran through the same lens as the U.S., and it is much less concerned that the Islamic Republic is a direct threat. And some experts believe the U.S. is putting too much hope on its diplomatic abilities. Obama administration officials justified the new missile defense stance in part by what they said was a new intelligence assessment that Iran's development of its long-range missiles was slowing. But that assertion surprised some experts. Trey Obering III, a retired Air Force lieutenant general and the former head of the Missile Defense Agency, said Iran's satellite launch and solid rocket tests this year signaled to him that Iran was continuing to make progress. 'I am very surprised by the new intelligence assessment. It is dramatically different from what we were told last spring. To me it flies in the face of what is observable,' Obering said. Obering said he believes the Obama administration is counting on the decision to cancel the ground-based interceptors to give a boost to a diplomatic offensive. That strategy, he said, could be risky, as the nation learned through the Clinton administration's ultimately unsuccessful efforts to halt North Korean weapons programs. 'They are counting very heavily on Russia being able to influencing the Iranians to disarm or not pursue nuclear program. There are a lot of eggs in that basket,' he said. Administration officials insisted they were not abandoning missile defense, contending the new system would defend better against immediate threats and that planned technological developments would enable the system to counter longer-range weapons. 'None of what was decided on missile defense was predicated on the notion that you could solve the problem through diplomacy and therefore you could take a risk,' said one official, who declined to be named because he was not authorized to speak for the record. The Obama administration has pushed to 'reset' relations with Russia. Cancelng a project that Russia viewed as a direct threat was a dramatic gesture. But it is not clear how much assistance Moscow is willing to offer the U.S. in pressuring Iran. The Kremlin has given signs of expecting wholesale U.S. policy shifts without having to make any equivalent compromises. 'The latest decision by President Obama ... has positive implications,' said Putin, who is regarded as the most powerful Russian official, in remarks carried on state media. 'And I very much hope that this very right and brave decision will be followed by others.' Dimitri K. Simes, president of the Nixon Center and an expert on Russia, said senior Russian officials had made clear privately that if they believed a genuine partnership with the U.S. was in the offering, they could be 'somewhat more accommodating' on Iran. Obama and Russian President Dmitry Medvedev are due to meet at the United Nations on Wednesday, and Simes predicted that Russia would back some sanctions against Iran, even if it continued to oppose sweeping economic restrictions. 'We have the right signals coming from Moscow,' he said. The administration official said that there had been no discussions with the Russians about tying a tougher stance on Iran to the U.S. shift on missile defense. 'I don't know, and I don't think any of us know, what the Russian current thinking is vis-a-vis imposing greater sanctions on Iran. We haven't gone to them to request it,' the administration official said. In Brussels, the new NATO secretary-general, Anders Fogh Rasmussen, said disagreements between Russia and the alliance would not disappear overnight. 'However, I do believe that it is possible for NATO and Russia to make a new beginning and to enjoy a far more productive relationship in the future,' Rasmussen said. Rasmussen called on NATO and Russia to expand their cooperation in fighting terrorism, halting weapons proliferation and in missile defense. 'Both NATO and Russia have a wealth of experience in missile defense,' he said. 'We should now work to combine this experience to our mutual benefit.' In a news conference in Brussels, Russia's envoy to NATO, Dmitry Rogozin, called Rasmussen's comments positive and constructive. In response to the U.S.' moves, Russia will cancel plans to field short range missiles near Poland, Rogozin said, suggesting that further joint work on missile defense was possible. 'Cooperation with Russia is not a matter of choice but of necessity,' he said. Times staff writers Barnes reported from Washington and Stack from Moscow. 