Hillary Clinton reflected on her accomplishments as Secretary of State over the last four years in a wide-ranging speech on foreign policy trends on Thursday.

She also touched on what she sees as America's most pressing global challenges in the future, signaling that her time in the Obama administration is drawing to a close.

At the top of her remarks given at the Newseum in Washington D.C., Clinton took a moment to address the U.N. resolution passed in the General Assembly just minutes before she spoke that recognized Palestine as a non-member observer state. She called the measure "unfortunate and counterproductive," reiterating her warning earlier in the day that peace between Israel and the Palestinians would come through direct negotiations, not international resolutions.

"We have been clear that only through direct negotiations between the parties can the Palestinians and Israelis achieve the peace they both deserve: two states for two people with a sovereign, viable independent Palestine living side-by-side in peace and security with a Jewish and democratic Israel," said Clinton.

The overall theme of Clinton's address however, was that economic and diplomatic challenges across the globe are changing the way the United States relates to both allies and foes.

"We do live in a rapidly changing world. Many of the constants that shaped American foreign policy for decades are shifting. And that poses new challenges for our global leadership," she told the crowd.

Among those changes, she said, are the economic crises shaking allies in Europe, China's continued rise as a global power, regime change in the Arab world as the U.S. works towards energy independence, a greater emphasis on strength through economics rather than arms, and a new generation growing up without the same pro-American sentiment held by their parents and grandparents. Clinton reflected on her travels to more than 112 countries, calling it "shoe-leather diplomacy," and emphasizing the importance of being on the ground.

"I have found it highly ironic that, in today's world, when we can be anywhere virtually, more than ever people want us to show up, actually," she said. "Somebody said to me the other day, 'I look at your travel schedule. Why Togo? Why the Cook Islands?' No secretary of state had ever been to Togo before. Togo happens to be on the U.N. Security Council. Going there, making the personal investment, has a real strategic purpose."

Among her accomplishments, she listed hosting town halls with global youth, raising awareness for religious minorities, protecting Internet freedom and advancing rights for women and the LGBT community around the world.

Clinton also reflected on arguably the darkest chapter of her tenure - the Sept. 11, 2012 attack on the U.S. consulate in Benghazi, Libya, that killed four State Department employees, including the U.S. ambassador to Libya, Christopher Stevens. Clinton increased security at American embassies and consulates across the globe as a result of the attack, but reiterated that diplomats serving in dangerous places must continue to exist for American diplomacy to work.

"As we mourn fallen friends like Ambassador Chris Stevens, who was fearless in his dedication to diplomacy, we refuse to be intimidated. Our people cannot live in bunkers and do their jobs," Clinton said. "So we will do what we always have done: pull together, learn and improve - because America always emerges stronger and more confident."

During a question-and-answer session following her speech, Clinton discussed the current and future challenges for America on the horizon.

She was asked about the conflict in Syria and whether it had reached a tipping point. While Clinton agreed the rebels had grown stronger and more unified, she stopped short of saying the country was were turning in the opposition's favor.

"It appears as though opposition in Syria is now capable of holding ground, and that they are better equipped and more able to bring the fight to the government forces, and so we follow closely where the government still maintains regime control and where it's contested and where the opposition is making significant inroads," Clinton said. "I don't know that you can say that for the entire country there is yet a tipping point, but it certainly seems that the regime will be much harder-pressed in the next months."

On U.S. engagement with Iran, Clinton said time is running out for Tehran to respond to the international community's diplomatic efforts. Ambassador Robert Wood reportedly told the International Atomic Energy Agency board in Vienna on Thursday that the United States has set a March deadline with Iran to start cooperating with the agency or else the issue will be referred to the U.N. Security Council - a significant step towards ending diplomacy and heading towards intervention.

"I think what was meant about the March reference was either about the IAEA and its continuing work or the fact that we finished our election and now would be a good time to test the proposition that there can be some good-faith, serious negotiations before the Iranians get into their elections, which are going to heat up probably around the March period, heading toward a June election," said Clinton.

"I think that we'll see in the next few months whether there's a chance for any kind of serious negotiation," she said. "And right now, I'm not sure that it can happen, but I certainly hope it does."