Secretary of State Hillary Rodham Clinton will confer later this week with NATO nations and others prosecuting an air campaign in Libya that has recently become more intense and apparently more focused on Libyan strongman Moammar Gadhafi.
Clinton was heading for the United Arab Emirates, where she and other members of the so-called Contact Group on Libya will assess the effort to get Gadhafi to leave and increase support for the country's opposition.
NATO has stepped up its operation this week, launching a ferocious series of nearly 30 daytime airstrikes on Tripoli to limit Gadhafi's ability to fight the rebels and attack civilians.
Gadhafi responded by angrily denouncing the rebels and vowing not to surrender.
The meeting Clinton is to attend Thursday in Abu Dhabi is aimed at refining the strategy and setting the stage for a post-Gadhafi Libya despite his refusal to back down and attempts to crush the rebels.
"Gadhafi must step down and hand power to the Libyan people, and the pressure will only continue to increase until he does," President Barack Obama said Tuesday at a news conference with visiting German Chancellor Angela Merkel.
He noted that Gadhafi's troops had been forced to retreat in many areas in what appears to be an "inexorable trend of the regime forces being pushed back, being incapacitated. "
"I think it is just a matter of time before Gadhafi goes," Obama said.
Germany is not part of the NATO operation, but Obama praised the country for contributions elsewhere that have allowed other allies to free up assets to participate. He also said that Germany could play a major role in helping Libya rebuild and put together a democratic government when Gadhafi eventually goes.
Merkel agreed and said: "Gadhafi needs to step down and he will step down."
Meanwhile, a Senate resolution backing limited U.S. involvement in the NATO-led military campaign against Libya was in doubt amid uncertainty and divisions among lawmakers over the next step.
The Senate Foreign Relations Committee abruptly postponed action on the resolution scheduled for Thursday. Senate Foreign Relations Committee Chairman John Kerry, D-Mass., Republican Sen. John McCain of Arizona and several other senators had introduced the nonbinding measure last month that supports the limited use of military force and concurs with Obama that the stated goal of U.S. policy "is to achieve the departure from power of Moammar Gadhafi" for the transition to an inclusive government.
The U.S. and the mainly European members of the Contact Group may be looking at the endgame in Libya, but Gadhafi himself appeared far from ready to concede on Tuesday.
In a phone call to Libyan state television station, Gadhafi said he would not give up.
"We will not kneel!" he shouted. "We will not surrender: we only have one choice _ to the end! Death, victory, it does not matter, we are not surrendering!" he shouted.
"We are stronger than your weapons, than your planes. The voices of the Libyan people are stronger than the sounds of explosions," he said, angrily calling the rebels who have risen up against him "bastards."
The main opposition group, the Benghazi-based Transitional National Council, has been appealing for diplomatic recognition and financial support with mixed results. Although a few countries have recognized the council as the legitimate government of Libya, the United States and several other key states have not.
The U.S. has provided some assistance to the rebels but has not yet acted on requests to free up some of the more than $30 billion in Gadhafi regime assets it has frozen to provide help to the Libyan people.
Clinton probably will hear renewed calls from council members for assistance.
After the Libya meeting, Clinton will tour Africa, visiting Zambia, Tanzania and Ethiopia, to promote trade, development and women's health and empowerment. She will also hold talks on the situation in Sudan.