Updated

President Bush said Thursday that the United States is seeking a diplomatic solution to the nuclear standoff with North Korea, but cautioned that diplomacy will take time.

Bush said he was pleased that leaders of China, South Korea, Japan and Russia, in telephone calls during the past few days, agreed that the reclusive communist regime should not be allowed to possess nuclear weapons.

"My message was that we want to solve this problem diplomatically, and the best way to solve this problem diplomatically is for all of us to be working in concert," Bush said.

Bush said the nations' message to Kim Jong Il was, "We expect you to adhere to international norms. We expect you to keep your word."

He said that what's important is that the international community speak with one voice.

"Diplomacy takes a while," he said, "We're spending time, diplomatically, making sure that voice is unified."

"Let's send a common message that you won't be rewarded for ignoring the world and that you'll be isolated if you continue to do this and yet there's a way forward," Bush said.

At the United Nations, there were differences over a Japanese-backed draft resolution to sanction North Korea. U.S. Ambassador John Bolton said the measure had "broad and deep support," but Russia's deputy U.N. ambassador told The Associated Press that Moscow would not back sanctions, as the resolution calls for.

Click here to read about North Korea's threat to fire more test missiles.

Instead, Russia wants the council to pass a nonbinding presidential statement with the goal of getting North Korea back into six-party talks on its nuclear program.

While agreeing that North Korea's missile tests were a provocative act, Canadian Prime Minister Stephen Harper, who appeared with Bush at the news conference, said Canada was not ready to reopen discussions about joining the U.S. missile shield.

The shield involves basing missiles capable of taking out incoming missiles launched by terrorists or rogue states — although the system is not designed to foil a mass attack by a major power.

Opponents of the missile scheme — including Canada's former Prime Minister Paul Martin — say it will not work and risks kicking off a new international arms race. Bush said he did not broach the issue with Harper.

"I didn't bring it up," Bush said. "I figured if he was interested, he would tell me."

Bush said the more isolated North Korea becomes, the bigger the threat is to the world.

"It's hard for me to tell you what's on his mind," Bush said. "This is a very closed society. We do know there are a lot of concentration camps. We do know people are starving.

"I think what we have to do is plan for the worst and hope for the best."