WASHINGTON — As the White House deals with the diplomatic repercussions of an intelligence estimate challenging its statements about Iran’s development of nuclear weapons, the administration is facing a new challenge on its policy toward the other remaining member of President Bush’s “axis of evil,” North Korea. The assistant secretary of state for East Asian and Pacific Affairs, Christopher Hill, said yesterday that Pyongyang likely would not meet a December 31 deadline to disclose the dismantlement of its nuclear facility at Yongbyon.

He added that he did not expect the fuel from Yongbyon to be removed by the end of December, and speaking about a North Korean draft declaration on its weapons program, he said it had fewer elements than America would like to see.

Mr. Hill also confirmed that President Bush on December 1 sent a letter to Kim Jong Il and other heads of state represented in the six-party nuclear negotiations process.

While Mr. Hill declined to provide the details of the letter, the fact that it was sent is significant. In 2004, President Bush remarked about North Korea’s gulags and how they could be seen from space.

In an interview in 2003 with Bob Woodward of the Washington Post, Mr. Bush expressed loathing for the North Korean dictator.

A spokesman for the National Security Council, Gordon Johndroe, yesterday issued the following statement on the letters: “In these letters, the president reiterated our commitment to the six-party talks and stressed the need for North Korea to come forward with a full and complete declaration of their nuclear programs, as called for in the September 2005 six-party agreement.”

Mr. Hill said he was pleased with the progress of North Korea’s cooperation in dismantling the components of their Yongbyon reactor.

The developments in American policy toward Pyongyang and Tehran illustrate in many ways the collapse of the original Bush doctrine that promised to keep the world’s most dangerous weapons out of the hands of the world’s most dangerous regimes. On Monday, the Office of the Director of National Intelligence released a new intelligence estimate of Iran’s nuclear weapons program concluding with high confidence that the regime’s enrichment of uranium at Natanz was separate from an effort to develop a nuclear weapon.

That estimate has already had a diplomatic ripple effect for American efforts to secure a third U.N. Security Council resolution against Iran for their enrichment activities at Natanz. The Chinese ambassador to the United Nations, for example, said this week that the estimate would force Beijing to re-evaluate its already tepid support for a third resolution.

Meanwhile, Russia’s foreign minister has said the new estimate makes the diplomatic push against Iran less urgent.

America’s European allies still are publicly backing the president’s diplomacy. At a joint press conference in Paris with President Sarkozy of France, Chancellor Merkel of Germany said, “Iran continues to represent a threat.” Behind the scenes, however, German diplomats have indicated they would not support European or unilateral divestment from Iran, a key objective of the American diplomatic push.

The deputy intelligence chief at the Office of the Director of National Intelligence, Donald Kerr, yesterday defended his report before the House Permanent Select Committee on Intelligence. He said the estimate had thousands of sources.

But Mr. Kerr also said Iran continued work on what he called “the most important component” of a future weapons system, the development of highly enriched uranium.