The international community Thursday expressed regrets over the resignation of Kofi Annan, who was appointed by the UN and the Arab League as a joint special envoy for Syria earlier this year.

In a statement released by his spokesperson, President of the UN General Assembly Nassir Abdulaziz Al-Nasser commended the relentless efforts of Annan over the past five months to fulfill the mandate of the UN General Assembly.

Al-Nasser said he understood how difficult Annan's task had been.

"Annan's well-known experience, wisdom and worldwide credibility were invaluable assets in his difficult mission," he said, calling again on the international community to fully unite to put an end to the violence in Syria and find a peaceful solution to the crisis.

China expressed on Thursday regret and understanding over Annan's resignation.

"We understand the difficulties Mr. Annan has encountered in negotiation work and we respect his decision," Ministry of Foreign Affairs spokesman Hong Lei said, adding that China appreciates the active and constructive role Annan has played in pushing forward the political process of the Syrian issue.

Hong said China is committed to the peaceful, fair and appropriate resolution of the Syrian issue, and that the international community should stick to the political settlement of the issue.

"China is open to any proposal that can help politically solve the Syrian issue, and China supports the United Nations to continue to play an important role in achieving the resolution," Hong said.

In Brussels, European Union (EU) foreign policy chief Catherine Ashton said the EU will continue to support a peaceful political transition in Syria.

Ashton said in a statement that she deeply regretted the resignation of Annan, who was appointed to the role on Feb. 23 to find a solution to the crisis in Syria.

"The EU continues to support the efforts of the UN and the Arab League, and calls for the early appointment of a successor to carry on Mr. Annan's work towards a peaceful political transition in Syria," she said.

"The Six Point Plan remains the best hope for the people of Syria, and any further militarization of the conflict by any of the parties can only bring greater suffering to Syria, its citizens, and the region as a whole," Ashton added.

She said the EU remains committed to pursuing a Syrian-led political transition to the crisis that would meet the democratic aspirations of the Syrian people and bring back stability to the country.

Also on Thursday, the United States again ruled out arming the opposition in Syria after Annan announced his resignation.

"Our position has not changed," White House spokesman Jay Carney told reporters aboard Air Force One en route to Orlando, Florida.

"We provide non-lethal assistance to the opposition. We don't believe that adding to the number of weapons in Syria is what's needed to help bring about a peaceful transition," he said.

He noted that U.S. President Barack Obama is "grateful" for Annan's willingness to serve as UN-Arab League joint envoy and for his efforts to achieve peace and a peaceful transition in Syria.

U.S. Secretary of State Hillary Clinton, currently on an African tour, said her country remains committed to an "effective and swift" political transition in Syria as envisioned by Annan.

"We remain committed to an effective and swift political transition as envisioned under the Annan framework," the top U.S. envoy said in a statement.

Clinton added that she spoke to Annan over telephone earlier in the day, thanking him for his service as the UN-Arab League joint envoy.

Vitaly Churkin, Russia's envoy to the UN, also said he "regretted" the resignation of Annan and offered gratitude to his mediation efforts.

One of the reasons that Annan's diplomatic efforts have gone through many difficulties is that his appeal for no further militarization of the Syrian conflicts was not really heeded by some influential countries in the international community, Churkin said.

In Damascus, the Syrian Foreign Ministry reiterated the country's commitment to Annan's peace plan, stressing the leadership's belief in national dialogue as the sole way to exit the current crisis without any foreign intervention.

Some countries that voted in favor of Annan's plan are the ones that hindered the plan, "because their intentions haven't ever been truthful," the ministry said in a statement.

Meanwhile, prominent Syrian opposition figures said Annan's resignation means the failure of his peace initiative to bring the Syrian crisis to an end.

Hasan Abdul-Azim, head of the National Coordination Body, said Annan's plan faltered from the very beginning due to the non-stop violence, which has recently dramatically escalated to an all-out urban battle.

"All hopes for political solutions have stopped," he said, adding that the situation in Syria is veering toward a civil war.

"This would jeopardize the unity of the Syrian people, the national facilities and institutions as well as the sovereignty of the homeland," Abdul-Azim said.