Russian Foreign Minister Sergei Lavrov, left, and U.S. Secretary of State John F. Kerry in Beijing. (Nicholas Kamm/Reuters)

Secretary of State John F. Kerry said Saturday that the United States and Russia will keep talking about the deteriorating situation in eastern Ukraine, although he made clear that Washington does not accept Moscow’s denial of involvement in the arming of pro-Russian rebels.

“Suffice it to say that we do have some disagreements about some of the facts on the ground with respect to Ukraine,” Kerry said after a meeting with Russian Foreign Minister Sergei Lavrov. “We have agreed to exchange some information between us regarding that. We have also agreed this is a dialogue between us that will continue.”

Kerry met with Lavrov in Beijing a day after Ukraine asserted that 32 Russian tanks and a similar number of other Russian military vehicles had entered the country’s eastern Luhansk region, ferrying ammunition and reinforcements to pro-Russian separatists opposed to the government in Kiev. The incursion, if verified, raises questions about Russia’s support of a cease-fire.

Minutes before the two top diplomats sat down, while shaking hands before cameras, Lavrov sidestepped a question about whether Russia is sending troops and tanks into Ukraine.

“Even Jen Psaki said that the State Department doesn’t have the information about this,” he said, naming the State Department spokeswoman who is often scapegoated in Russia’s state-owned media for her criticisms of Russia’s actions in Ukraine. Pressed for details, Lavrov replied, “Well, if Psaki doesn’t have it, I don’t.”

Moscow has denied arming and supplying the rebels and has called Ukraine’s latest charges a provocation fueled by social media rumors.

Kerry is heading to Oman to meet with Iranian Foreign Minister Mohammad Javad Zarif and Catherine Ashton, the European Union’s foreign affairs chief, who is usually present when the United States’ and Iran’s top diplomats confer. They face a Nov. 24 deadline for a landmark deal to impose significant reductions on Iran’s nuclear capabilities and, in return, gradually free Iran from sanctions.

Lavrov told the Russian news agency Interfax that Moscow shares Washington’s view that the deadline can be met, with only two or three issues outstanding. However, the substance of those differences is huge.

In a report made public Friday, the International Atomic Energy Agency said Iran still has not provided information that would allay suspicions it is working to produce nuclear weapons.

The watchdog agency said that it is confident that none of the nuclear material Iran has acknowledged having has been diverted for possible military use but that it cannot verify that Iran may have some covert supplies it has not reported.

It also said that while Tehran remains committed to cutting back its nuclear capacity, it has failed to provide a full accounting of its previous nuclear work. Iran insists its nuclear industry is intended solely for peaceful purposes such as energy and anti-cancer medical treatments.

Some nuclear experts are skeptical that the United States and five other nations negotiating with Tehran will secure enough assurances for an agreement by the deadline, barely two weeks away.

In his remarks to reporters in Beijing, Kerry sought to tamp down reports that President Obama wrote a letter last month to Iran’s supreme leader, Ayatollah Ali Khamenei, linking cooperation in the fight against the Islamic State in Syria and Iraq to a nuclear deal. Without confirming the letter’s existence, first reported by the Wall Street Journal, Kerry denied that the United States had made any promises tying the two issues.