COPENHAGEN -- He came, he saw, he didn?t conquer. The most anticipated event of the entire two-week-long climate change conference in this icy Danish capital was US President Barack Obama?s speech, which many negotiators hoped would drive the newly re-started talks to a successful conclusion. Instead, it may have had the opposite effect.

The speech was delayed by about two hours, because Obama had plunged into direct negotiations immediately after arriving in this city. The abrupt change in schedule left many world leaders cooling their heels or making small talk inside the main plenary hall.

When he finally spoke, almost all activity in the sprawling conference venue came to a stop; those outside the hall formed scrums around the closed-circuit TV monitors.

After high-impact appearances by US Sen. John Kerry, who pledged a climate bill will pass the US Senate next year; and by US Secretary of State Hillary Clinton, who signaled US preparedness to help raise $100 billion a year by 2020 to help developing economies adapt to climate change, Obama was widely expected to make a forceful speech and possibly even a dramatic announcement.

In the eyes of many delegates, he did neither.

He restated American positions on the climate change negotiations, took aim at China by raising the issue of transparency in monitoring compliance with emission reduction targets and ended with a general call for action.

The effect was as though the Kerry and Clinton visits had not occurred, and as though China had not responded to Clinton's announcement with some concessions on their position on verification.

The disappointing speech had many critics, none more biting than Hugo Chavez, the president of Venezuela. He called Obama's remarks "ridiculous," and chided those who had looked to Obama for leadership. Obama was "one of the greatest frustrations" because people had believed in him, he said.

Obama's speech effectively cost the rollercoaster conference its momentum. Very few leaders now hold out hope that a substantial political agreement will be reached before the end of the day.