BUCHAREST, Romania — President Bush expressed confidence Wednesday that NATO will bolster its combat forces in Afghanistan and endorse a missile defense system for Europe that Russia has opposed.

"I'm optimistic that this is a going to be a very successful summit," Bush said, sitting alongside NATO Secretary-General Jaap de Hoop Scheffer hours before the 26-nation military alliance opened three days of meetings with a leaders' dinner.

The summit has been troubled by divisions, most notably opposition from France and Germany to giving Ukraine and Georgia a plan for eventually joining NATO. Bush indicated that was an open question because any NATO member can block it.

"We'll see," he said, saying one country was still an issue.

Bush has been pushing NATO countries to commit more troops to the 47,000-strong NATO force in Afghanistan. At least 10 countries, including France, Germany, Norway and Poland, have announced they would do so, but Bush would like to see more.

"I feel good about what I'm hearing from my fellow leaders about their desire to support Afghanistan," the president said. "I think if tomorrow we get clarification on troop support ... the people of Afghanistan are going to be more than grateful." He did not mention any specific numbers of additional troops.

The U.S. is the biggest contributor of troops in Afghanistan, with 17,000 in the NATO-led force and 14,000 in a U.S.-led contingent in eastern Afghanistan that trains Afghan forces and hunts al-Qaida fighters. The U.S. presence is set to go up by 3,500 Marines, most of them dedicated to the NATO mission.

Bush has spent months trying to persuade Russia that it has nothing to fear from a missile defense shield in Europe, based in Poland and the Czech Republic.

He said "it looks like to me that the agreement is coming together" within NATO at least to support a defensive system. The president is to meet with Russian President Vladimir Putin on Sunday in the resort city of Sochi, and the White House has held out hopes of an agreement easing Russia's opposition to a missile shield.

Putin, Bush said, should "welcome NATO because it is a group of nations dedicated to peace."

De Hoop Scheffer told Bush, "I can share and echo your optimism." He said NATO would "take a clear position on missile defense."

The NATO chief also said the alliance would publish a so-called "vision statement" about expanding its traditional role "the front lines in the fight against terrorism."

De Hoop Scheffer was optimistic about adding new members to NATO. Croatia, Albania and Macedonia are hoping to get invitations this week, although Greece may block Macedonia.

Taking note of the dispute over Ukraine's hopes for eventual membership, de Hoop Scheffer said, "I think this can never be a question of whether ... I think the door should be open." But he did not say whether Ukraine's chance to start the process, along with Georgia, would come now or have to wait.