Sen. John McCain on Monday faulted President Trump's team for failing to "develop a strategy for success" in Afghanistan, even as threats in the country grow.

"After nearly 16 years of war, we are at a stalemate in Afghanistan," the Arizona Republican and chairman of the Senate Armed Services Committee said. "Worse, we have no strategy to end that stalemate and achieve victory."

McCain's criticism is an escalation of congressional frustration with the Trump administration's handling of Afghanistan. McCain has been willing to criticize Trump, but has often has tempered his misgivings by emphasizing his confidence in Defense Secretary Jim Mattis and the other members of Trump's national security team. But those sentiments were absent from Monday's warning.

"Mattis testified before the Senate Armed Services Committee last week that we are not winning in Afghanistan," McCain said. "And yet, six months into the new administration, it still has not delivered a strategy. We cannot keep going like this. If the administration fails to develop a strategy for success, Congress will need to play a greater role."

Lawmakers usually give presidents a wide berth in setting foreign policy, but such an intervention into the Afghanistan policy process would be the latest attempt to take the reins from Trump. It comes on the heels of an overwhelming majority of senators voting in favor of a strict Russia sanctions package, even after Secretary of State Rex Tillerson signaled that the administration believes the bill would tie its hands.

"I would urge Congress to ensure any legislation allows the president to have the flexibility to adjust sanctions to meet the needs of what is always an evolving diplomatic situation," Tillerson told the House Foreign Affairs Committee at the opening of a hearing on the State Department's budget request. "Essentially, we would ask for the flexibility to turn the heat up when we need to, but also to ensure that we have the ability to maintain a constructive dialogue."

U.S.-Russia relations took a turn for the worse in Syria, after a U.S. fighter shot down a Syrian warplane in response to attacks on the U.S.-led coalition to defeat the Islamic State. Russia responded by declaring vast swathes of Syria off-limits to American planes. But lawmakers worry that Trump lacks an effective strategy in Syria as well.

"I believe that we'll continue to take out ISIS leadership and create havoc for ISIS and al Qaeda in the region; however, you take the longer term risk of empowering the [Iran-backed] Shias and the Russians and the Assad regime to create more havoc for the West," House Intelligence Chairman Devin Nunes, R-Calif., told the Washington Examiner.