ST. PETERSBURG, Russia (AP) — "Toxic" political infighting is preventing U.S. President Donald Trump from improving relations with Moscow, Russia's former ambassador in the United States and a long-time Trump campaign contact told The Associated Press on Friday.

Ties between the two countries have deteriorated steadily since Russia annexed the Crimean Peninsula and threw its weight behind separatists in eastern Ukraine. Moscow's hopes that Trump would be willing to improve the relationship have been largely disappointed.

Sergei Kislyak, who served as Russia's ambassador in Washington from 2008 until his tenure ended last year, told the AP that Trump appears eager to improve ties but a bad political climate is making that impossible.

"In the current environment, even for the president, who is interested in improving ties with Russia, it's not that easy to do because of the legislation and the political climate, which is toxic," he said.

Kislyak was called off last August amid scrutiny of his recurrent meetings with the Trump campaign staff as Special Counsel Mueller's probe into the possible Russian meddling was gaining speed.

The long-serving diplomat popped up on the FBI's radar after maintaining contact with Trump aides during the campaign and immediately after the 2016 election. After Trump's election, Kislyak spoke by phone several times with White House national security adviser Michael Flynn and discussed sanctions put in place by the Obama administration. The calls were monitored by U.S. intelligence agencies, and days after Trump took office in January 2017, Flynn was interviewed by FBI agents about those talks. He acknowledged as part of his plea to lying during that interview.

Speaking on the sidelines of Russia's showcase economic forum in St. Petersburg, Kislyak, who now sits in the upper chamber of Russia's parliament, expressed hope that mutual business interests will help overcome the bitter strain between Russia and the U.S.

"Economy has been chosen as a tool of political leverage," Kislyak said. "They (Americans) are cutting the branch of the tree they're sitting on with those sanctions."

After he became president, Trump not only did not lift the sanctions imposed on Russia by President Barack Obama but approved several more rounds of restrictions, including expelling Russian diplomatic staff from the U.S. and targeting some of Russia's richest men, including billionaire Oleg Deripaska and his aluminum company Rusal. Rusal was cut off from international financing and left Deripaska scrambling to try to get the U.S. to roll back the sanction.

Viktor Vekselberg, another Russian billionaire who had to cut his share in some of his overseas holdings to shield them from U.S. sanctions, on Friday spoke in favor of maintaining ties between Russia and the U.S.

"We need to talk — we have nothing else left to do," he told a panel at the St. Petersburg forum. "We need to use all channels, all opportunities to keep the precious little that is left between our two countries."

A company associated with Vekselberg routed money to Trump lawyer Michael Cohen's consulting firm last year, according to documents reviewed by the AP. Vekselberg refused to comment on these reports when approached by the AP on Friday.

In reaction to the new sanctions, Russia's parliament last month floated a bill that threatens to freeze key exports to the U.S., crippling long-standing business deals and hitting industries jobs both at home and abroad. The original bill alarmed Russian industries as it proposed tough restrictions, including a ban on exports to the U.S. of titanium.

Under pressure from business groups, the lawmakers toned the bill down and got rid of references to specific restrictions. The watered-down version was passed this week.

Sergei Kravchenko, president of Boeing's Russia venture, which would have been hit hard by the bill, told the AP that the deliberations were a "worrying moment for his company."

Kravchenko said he was encouraged that Russian leaders eventually recognized that it was "foolish" to hurt Russian industry by blocking exports "because of some emotions on the spur of the moment."

Russian Deputy Prime Minister Dmitry Kozak seemed to agree, warning Friday against "slaughtering the chicken that lays golden eggs."