NEW : Russian , Polish leaders cautiously optimistic about U.S. commitment . President Obama on Thursday says the Bush-era missile defense plan will be replaced with a new system . Czech president : ` ` We appreciate the responsible approach '' of U.S. leader . Defense chief Fischer denies U.S. `` scrapping '' missile defense . Change of gears does creates diplomatic problems for The Islamic republic 's , expert says .
NEW : Russian , Polish leaders cautiously optimistic about U.S. commitment . Czech president : `` We appreciate the responsible approach '' of U.S. leader . Defense chief Fischer denies U.S. `` scrapping '' missile defense . Change of gears does creates diplomatic problems for The Islamic republic 's , expert says .