President Bush encountered resistance on his climate-change policy as he and other world leaders sought to strike a balance between framing a deal on global warming while coping with inflation and slumping economic growth.

Building a consensus was not proving easy for him as the Group of Eight economic powers planned to turn its attention tomorrow to global warming, soaring food and fuel costs, and world conflicts.

Beyond the climate-change standoff, Mr. Bush’s proposal to base a missile defense system in Eastern Europe was rebuffed today by Russia’s new president, Dimitry Medvedev. And Mr. Bush failed to achieve a consensus among African leaders on sanctions against the government of Zimbabwe’s Robert Mugabe to protest his widely condemned re-election last month after his opposition-party rival dropped out, fearful for his life.

“You know I care deeply about the people of Zimbabwe,” Mr. Bush told reporters after a meeting today with African leaders who were invited to meet with summit partners. “I’m extremely disappointed in the elections, which I labeled a sham election.”

Separately, Chancellor Merkel of Germany said Mr. Mugabe’s election was not legitimate. “As for us in Germany, we do not rule out further sanctions,” she said, adding that many other G-8 nations feel the same way.

But African nations are deeply divided, with many reluctant to put public pressure on Mr. Mugabe despite United Nations and Western calls for tough action.

“There were differences. Not all leaders are there yet in terms of sanctions,” a White House national security aide, Dan Price, said.

The big issue on tomorrow’s agenda was climate change; it was certain to be a major topic when Mr. Bush meets one-on-one with Ms. Merkel, one of the G-8’s strongest advocates for tough reductions in the emissions that contribute to global warming.

She succeeded in winning his backing last year, when the summit was held in Germany, to a statement pledging that the group would seriously consider a goal of halving greenhouse-gas emissions by 2050 — while failing to persuade him to commit to more specific targets.

Now, as then, Mr. Bush is insisting that major emerging economies like China and India be included in any plan to cut emissions. But they have so far resisted. Adding to Mr. Bush’s isolation on the issue, the European Commission President, Jose Manuel Barroso, said G-8 nations must reach agreement among themselves and avoid taking the approach that “I will do nothing unless you do it first,” which he called a “vicious circle.”

Still, Mr. Bush has come a long way since his first G-8 summit when he held that evidence was not conclusive that man’s activity contributed to the warming of the Earth’s climate.

The G-8 — America, Japan, Russia, Britain, Germany, France, Italy, and Canada — takes up the subject in earnest tomorrow. On Wednesday, the leaders of these countries will be joined by eight other big-polluting “major economy” nations that are not members, including China and India, to see if a wider agreement is possible.

G-8 leaders are mindful that Mr. Bush’s days in office are numbered — and it seems likely they will await Bush’s successor rather than push for a strong commitment now.

Meanwhile, Ms. Merkel offered Germany’s support for an American initiative for a fund that would “promote climate-friendly technology until a follow-up treaty to the Kyoto Protocol would take effect.” That pact, which neither America nor India nor China has ratified, expires in 2012.

Furthermore, “even a new American administration” is going to insist that any climate agreement entail the principle that emerging economies must contribute to stemming global warming, Ms. Merkel said in an interview last week with The Associated Press.

Consensus remains elusive on climate change, acknowledged the chairman of the White House Council on Environmental Quality, Jim Connaughton.

“The president has made clear that we believe a long-term goal is useful and necessary,” Mr. Connaughton said. “The president has also made clear that it’s a goal that must be shared by all countries.”

Mr. Connaughton suggested that building more nuclear power plants was one way to help meet emission-reduction goals and reduce reliance on fossil fuels.

Meanwhile, Mr. Bush met with Mr. Medvedev today. The new Russian president signaled he was no more supportive of Mr. Bush’s plan to base parts of a missile defense system in eastern Europe than was his mentor, former president — and now prime minister — Vladimir Putin.

While agreeing with Mr. Bush on curtailing nuclear weapon capabilities of Iran and North Korea, Mr. Medvedev said there were other issues “with respect to European affairs and missile defense where we have differences.”

After the talks, a Kremlin aide said Messrs. Bush and Medvedev made no progress on missile defense.

Sergei Prikhodko said Russia is not yet satisfied with steps America has offered to take to ease Moscow’s concerns the system would be aimed at weakening Russia’s defenses. Mr. Medvedev also expressed serious concern about media reports that America has discussed the possibility of deploying interceptors in Lithuania, if its first choice of basing them in Poland doesn’t work out.

Poland’s foreign minister was in America for talks with Secretary of State Rice about Warsaw’s latest rebuffs to basing American missile interceptors at Poland for a future missile shield against Iran.

“This is absolutely unacceptable for the Russian Federation,” Mr. Prikhodko said of the Lithuanian plan. He said Mr. Medvedev also spoke to Mr. Bush about “the unacceptability” of former Soviet republics Georgia and Ukraine joining NATO, a move pushed by America.