PHNOM PENH, Cambodia — The top diplomats of the United States and Russia said Friday that their governments were ready to negotiate for Brittney Griner and Paul N. Whelan, two American detainees in Russia, through a channel earlier established by the their two presidents. The diplomats, Secretary of State Antony J. Blinken and Foreign Minister Sergei Lavrov of Russia, made their comments in separate news conferences with reporters a day after a Russian court sentenced Ms. Griner, a professional basketball star, to nine years in prison on a criminal colony. on charges of attempting to smuggle drugs into Russia. US officials have said Ms Griner has been “unlawfully detained” and that her trial was politically motivated as tensions between the two countries remain high over Russia’s war in Ukraine. The Biden administration has offered to free Victor Bout, a jailed Russian arms dealer, in exchange for Ms. Griner and Mr. Whelan, people familiar with the proposal said. Mr. Blinken and the State Department have not publicly disclosed details of the proposal. At a meeting of foreign ministers from East Asia and partner countries on Friday, Mr Lavrov said that although he and Mr Blinken had sat close to each other, Mr Blinken had made no attempt to speak together of. “Today, there was only one person among us at the table. I didn’t see him trying to grab me,” Mr Lavrov said at a news conference broadcast by the ministry. Asked this afternoon about Ms. Griner’s conviction and Mr. Lavrov’s claim that Mr. Blinken had not approached him, Mr. Blinken said only that talks would take place through the channel Mr. Lavrov cites. “We have put forward, as you know, a substantial proposal on which Russia will have to cooperate with us,” Mr. Blinken said. “And what Foreign Minister Lavrov said this morning, and he said publicly, is that they are ready to engage through channels that we have set up to do just that, and we will pursue that.” Mr Lavrov and Mr Blinken spoke last week about the possibility of a prisoner exchange, with negotiations taking place through a special channel set up for the purpose, according to people familiar with the conversation. At the time, Mr. Lavrov criticized the United States for what he described as an attempt to negotiate a public prisoner exchange. Both Mr Lavrov and Kremlin spokesman Dmitry Peskov renewed that criticism on Friday. “These exchanges will never happen if we start discussing any nuances of the exchange in the press,” Mr Peskov told reporters in Moscow. “The Americans made this mistake. They decided for some reason to solve these problems with the megaphone method.” Brittney Griner leaves the courtroom before the court’s final decision in Khimki outside Moscow on Thursday. Credit…Pool photo by Kirill KudryavtsevTrevor R. Reed in court in Moscow last year. Credit…Tatyana Makeyeva/Reuters In their diplomatic channel comments, both sides appeared to refer to an agreement between President Biden and President Vladimir V. Putin of Russia, reached at a summit in Geneva last June, to negotiate prisoner and hostage exchanges. Despite sending signals that a possible swap is possible, Russian officials have insisted that the legal process must be completed first. After hearing the verdict Thursday, Ms. Griner’s lawyers said they would appeal the sentence, which could further drag out the process. Trevor Reed, a former US Marine who was sentenced to nine years in prison after being accused of assaulting a Russian police officer, spent more than two years in Russian custody before being swapped for a convicted Russian pilot in April. Mr. Blinken said on Friday that Ms. Griner’s conviction “brings to the fore our very significant concerns about Russia’s legal system and the Russian government’s use of illegal detentions to advance its own agenda, using individuals as political pawns. The same goes for Paul Whelan.” Mr Whelan is a former US Marine who was convicted by a Moscow court of espionage charges in 2020 after first being detained in 2018. On Thursday, John Kirby, the White House national security spokesman, said he expected Mr. Blinken to try to talk with Mr. Lavrov about the American detainees during the meeting in Phnom Penh. “I have no doubt that if he has the opportunity to pin Mr. Lavrov, he will,” Mr. Kirby said. “And if it doesn’t, if it doesn’t just happen organically, I’m sure Secretary Blinken will reach out and have that communication.” When a conversation didn’t happen, Mr Lavrov appeared to try to tease Mr Blinken that he wasn’t talking to him, saying: “All my buttons are in place.” —Edward Wong and Ivan Nechepurenko