U.S. and Russian defense officials have concluded a third round of talks on rules for conduct in the air over Syria – and are finalizing a memorandum of understanding that will establish basic safety rules and avoid inadvertent collisions.
The U.S. Department of Defense said in a statement that "progress was made" during the video conference Wednesday, which "focused narrowly on the implementation of specific safety procedures."
The Russian Defense Ministry reported a "convergence" of positions "on key provisions of the future document."
Both parties agreed that the talks were "professional" and that the agreement is nearing completion.
WATCH: Video explainer about Syria situation
Russian Foreign Minister Sergei Lavrov said Wednesday that the United States declined to take part in broader talks about coordination in Syria that would have involved either country sending a high-level delegation to the other's capital.
A U.S. State Department spokesman said he did "not have anything specific" on the proposal. John Kirby also said the U.S. continues to show a willingness to talk with Russian authorities.
Russian President Vladimir Putin discussed the proposal at a forum on Tuesday, saying his side would have been led by Prime Minister Dmitri Medvedev and included military and security officials.
U.N. envoy for Syria Staffan de Mistura is pushing a separate effort to get the U.S. and Russia on the same page in working toward a broad political resolution to the crisis in Syria. He met with officials Tuesday in Moscow and was scheduled to hold talks Wednesday in Washington.
Meanwhile, Russia said its warplanes carried out at least 40 more bombing rounds Wednesday on Islamic State targets in the Syrian provinces of Aleppo, Idlib, Latakia, Hama and Deir ez-Zor.
Separately, Russia's Defense Ministry said one of its fighter jets approached a U.S. warplane in Syrian airspace last week only for identification purposes. Spokesman Igor Konashenkov said the Russian jet came within two to three kilometers of the U.S. plane in Aleppo province on a mission that was not intended to scare or provoke anyone. He said the Russian jet then returned to its fighting group.
Russian airstrikes have helped Syrian government troops regain territory, but the United States has criticized its campaign as targeting mostly rebel fighters and not Islamic State militants.
Reuters quoted two senior regional officials Tuesday as saying the Syrian army soon would launch an offensive on the northern city of Aleppo along with Russian air support and fighters from the Lebanese militant group Hezbollah and Iran. The officials cited a "large mobilization" of Syrian troops and thousands of Iranians.
Two prominent U.S. senators used the report to further criticize what they have characterized as a weak policy in Syria from President Barack Obama. Senators John McCain and Lindsey Graham, who have promoted sending U.S. ground troops to Syria, said the Aleppo offensive "would be the latest low point for the administration's disgraceful Syria policy."
Russian embassy hit
Also Tuesday, militants fired rockets at Russia's embassy in Damascus in what Lavrov, the foreign minister, called an "act or terror" meant to intimidate those who support the fight against the Islamic State group.
Two rockets struck the embassy compound while hundreds of people rallied outside in support of Russia. There was no word on damage or casualties.
The attack is not the only backlash against Russia. Security officials there said Monday they had arrested several people plotting to target the Moscow transportation system who had IS ties.
'Eye for an eye'
An Islamic State spokesman posted an online message Tuesday "calling on Muslims everywhere" to launch a jihad against Russia and the U.S. "Russia will be defeated," IS spokesman Abu Mohamed al-Adnani said in a recording posted online.
State Department correspondent Pam Dockins contributed to this report.