WASHINGTON -- Secretary of State Hillary Rodham Clinton said Thursday that both Iran and Russia continued to provide military support to the Syrian government led by President Bashar al-Assad and that there were indications that Iranian assistance was increasing.
The airstrike that Israel carried out on Wednesday in Syria on an arms convoy that was believed to be en route to Hezbollah militants in Lebanon, and Iran's subsequent warnings that the Israeli attack would lead to "grave consequences," have raised concerns that the conflict is becoming a regional one.
Mrs. Clinton, who will leave her State Department post on Friday, declined to discuss the Israeli operation.
But she noted that Iran appeared to have stepped up its aid to the Assad government, including the number of military advisers it was sending to Syria and the quality of military equipment it was providing.
"The Iranians have made it clear for some time that keeping Assad in power is one of their highest priorities," she said in her final meeting with reporters at the State Department. "There is a lot of concern that they are increasing the quality of the weapons because Assad is using up his weaponry. So it is numbers and it's matériel."
Russia's backing for Mr. Assad, she added, remains a worry as well.
"The Russians are not passive bystanders in their support for Assad," Mrs. Clinton said. "We have reasons to believe that the Russians continue to supply financial and military assistance in the form of equipment to Assad." Mrs. Clinton outlined her vision of diplomacy in a speech on Thursday afternoon at the Council on Foreign Relations here, repeating her themes that economic development and the use of social media were important complements to military force and the other more traditional levers of power.
"We face challenges, from financial contagion to climate change to human and wildlife trafficking, that spill across borders and defy unilateral solutions," she said. "The geometry of global power has become more distributed and diffuse as the challenges we face have become more complex and crosscutting."
But the immediate problems her successor, John Kerry, the former Massachusetts senator, will face after he is sworn in on Friday involve bitter military conflicts and looming confrontations, including the deteriorating situation in Syria, the diplomatic standoff with Iran over its nuclear program, the turmoil in Egypt and the emergence of affiliates of Al Qaeda in North Africa.
Iran and major powers have yet to settle on a site and date for resuming talks on the Iranian nuclear program.
"I don't think the window can remain open for too much longer," Mrs. Clinton said. "I am not going to put days, weeks or months on it."
Mrs. Clinton said she thought that there was much debate at the highest levels of the Iranian government on "how to maximize the leverage they have" in talks over the country's nuclear program, as well as political jockeying with an eye toward Iran's June elections, and that this had led to the delays in fixing a date for resuming negotiations.
As for American concerns about Russia, Vice President Joseph R. Biden Jr. is scheduled to fly to Munich this weekend for a security conference and is expected to meet there with the Russian foreign minister, Sergey V. Lavrov, on Syria and arms control issues. Mrs. Clinton said she believed that she had made headway with the Russians over the past year in fashioning a plan for a post-Assad transition in Syria. But it quickly emerged that the Russian government had not dropped its support for Mr. Assad.
Despite her complaints over continued Russian support for Mr. Assad, she voiced hope that the Russians would change their position.
Looking back on her years at the State Department, Mrs. Clinton said she had done everything she could to tamp down the Syria conflict by working to organize the Syrian opposition, backing humanitarian assistance and working to isolate Mr. Assad.
"I've done what was possible to do," Mrs. Clinton said.
At the same time, she acknowledged that the situation there had the potential to get much worse.
"The worst kind of predictions about what could happen internally, and spilling over the borders of Syria, are certainly within the realm of the possible now," she said.
This article originally appeared in The New York Times.