The U.S. will work with its allies to put "immense pressure" on Syrian President Bashar al-Assad to step down after Russia vetoed a resolution aimed at ending fighting, Secretary of State Hillary Clinton said.

"Faced with a neutered Security Council, we have to redouble our efforts outside of the United Nations with those allies and partners who support the Syrian people's right to have a better future," U.S. Secretary of State Hillary Clinton told reporters in Sofia Sunday. "Assad must go."

The U.S. will also work to strengthen sanctions against the Syrian government and "expose those funding Assad's regime," she said.

Russia and China Saturday vetoed a proposal by Western and Arab countries that backed an Arab League plan to facilitate a political transition in Syria. It was the second time Russia blocked attempts at the U.N. to hold Assad accountable for a conflict that the U.N. says has killed more than 5,400 people.

The veto gives Assad a "license to kill," Qatar's Minister of State for Foreign Affairs Khalid Al Attiyah said Sunday at a security conference in Munich. "Yesterday was a sad day," he said. "This is exactly what we feared."

Russian Foreign Minister Sergei Lavrov and the head of Russia's Foreign Intelligence Service Mikhail Fradkov will visit Damascus on Feb. 7 to meet with Assad, the Russian Foreign Ministry said in a statement on its website Sunday.

Russian weapons sales • Russia sells Syria weapons and has its only military base outside the former Soviet Union in the Syrian port of Tartus.

"The Russian government is not only unapologetically arming a government that is killing its own people, but also providing it with diplomatic cover," Philippe Bolopion, U.N. director at Human Rights Watch in New York, said after the vote Saturday.

Assad has blamed "terrorists" and foreign provocateurs for fomenting the protests, which began in March.

"The visit by Russian diplomats to Damascus next Tuesday indicates that Moscow knows the regime is in trouble," Andrew J. Tabler, a fellow at the Washington Institute for Near East Policy, said in response to emailed questions. "They want to try and see if they can prop it up by convincing it to reform — the one thing this regime has proven incapable of doing for over four decades."

Russian isolation • A measure of Russia's growing isolation is that South Africa and India, which had abstained in an October vote on Syria that was vetoed by Russia and China, Saturday broke ranks and sided with Arab and European nations.

Both countries took issue with Russia's claims that concessions made by Arab and European Union negotiators in the final draft could still be interpreted as calls for an Assad ouster.

"We thought we had a consensus text" and that "everyone was agreed," Indian Ambassador Hardeep Singh Puri said in an interview. The Russians wanted "another three days time but with the spiraling violence the council was not in the mood to countenance delayed action."

For both Russia and China to veto the resolution after the regime's assault on Homs and after Arab and Western allies diluted the resolution "effectively means they were helping Assad play for time and ensure his rule," according to Andrew J. Tabler, Syrian expert and fellow at the Washington Institute for Near East Policy.

Homs shelled • The Syrian army shelled the city of Homs, Al Arabiya television reported Sunday, citing activists. The Associated Press reported 30 people were killed across the country Sunday.

Syrian rebels killed nine soldiers in fighting overnight in Idlib, the U.K.-based Syrian Observatory for Human Rights said in an emailed statement Sunday. Twenty-one soldiers were wounded and four military vehicles were damaged, the group said. Syria halted operations at a sugar refinery in the central city of Homs due to security conditions, Al Arabiya television reported Sunday without saying where it obtain the information.

"The veto of the resolution on Syria will embolden Assad to even further brutalize his people," Paul Sullivan, a specialist in Middle East security at Georgetown University in Washington, said in an email. "There has been some consideration given to tightening sanctions, but without the arms embargo this will end up likely hurting the people it might be intended to help more than those in power."

"We are trying to start a process of political transition," Clinton said. "The failure to do so will increase the risk of a brutal civil war."

Doomed regime • U.K. Foreign Secretary William Hague said Syria's government was bound to fall and that the U.N. Security Council will return to the subject of violence in Syria. "This is a doomed regime, as well as a murdering regime," Hague told Sky News. "There's no way it can get its credibility back."

The Arab League in November imposed sanctions on the regime and sent monitors to the country in an effort to stop the violence. The league later drafted a plan that called for the formation of a national unity government within two months to implement a peaceful handover of power.

The Russian Ambassador to the U.N., Vitaly Churkin, said that, while he "would certainly agree tragic events are happening" in Syria, his country had "made an honest effort." He said the Arab League "shall not count on the Council" for endorsement of a plan that imposes a timeline on when Assad should leave.

Russia's alignment with Syria may put at stake the country's relationship with oil-rich Gulf States led by Qatar that asked the Security Council to endorse their plan to convince Assad to delegate his powers to a deputy to pave way for elections.

"The Russians are doing this to help preserve their navy base in Tartus, their arms trade with Syria and their strategic position in the Eastern Mediterranean," Sullivan said. "In the end Russia will lose its base. Russia has also in many ways lost the Arabs on this."

Flavia Krause-Jackson and Mourad Haroutunian contributed to this report.