Washington (CNN) President Donald Trump announced Wednesday he was lifting all sanctions on Turkey after it agreed to halt its attack on America's former Kurdish allies in northeastern Syria, shortly after his special envoy to Syria told Congress Turkey's incursion was a "tragedy" and that Ankara-backed forces are likely behind several war crimes.

Speaking in the White House Diplomatic Reception Room, the President claimed that "people are saying, wow, what a great outcome ... we've done a good job, we've saved a lot of lives." He praised President Recep Tayyip Erdogan, hinted that the Turkish leader would soon visit Washington and appeared to wash his hands of further US involvement in Syria.

"Let someone else fight over this long-bloodstained sand," Trump said, but added that some US troops would remain to protect oil in Syria, "and we'll be deciding what to do with it in the future."

Trump didn't mention Turkey's potential violations of international law, but shortly before he spoke, the US special envoy for Syria and the Global Coalition to Defeat ISIS, Jim Jeffrey, told the House Foreign Affairs Committee that the US believes Turkish-backed opposition forces in Syria have committed war crimes.

"We've seen several incidents which we consider war crimes," Jeffrey said.

"The Turkish incursion into northeast Syria is a tragedy. It was long-standing US government policy in two administrations to keep that from happening and we were clearly not successful," Jeffrey said.

Defense Secretary Mark Esper told CNN's Christiane Amanpour on Tuesday that NATO ally Turkey and its allies may be liable for war crimes based on reports he'd seen.

"They are horrible, and if accurate -- and I assume they are accurate -- they would be war crimes," Esper said. "I think those responsible should be held accountable. In many cases, it would be the government of Turkey."

The President spoke on Jeffrey's second day of congressional testimony to lawmakers united in bipartisan anger over his decision to pull back US troops from northeastern Syria. The decision was widely seen as a green light for Turkey's plan to attack the Kurds, a betrayal of a long-standing ally in the fight against ISIS and a damaging blow to US national security interests.

On Wednesday, however, the President said his administration had done a "good job," and claimed ISIS fighters who had escaped Kurdish jails after the Turkish attack have "been largely recaptured." He said the Kurds' military leader was "extremely thankful for what the United States has done" and has assured the US "that ISIS is under very, very strict lock and key."

An hour earlier, Jeffrey told House lawmakers that the US now estimates that over 100 ISIS fighters had escaped and that "we do not know where they are."

'A victory for them'

Asked how the US pullback had impacted the terror group's recruiting, Jeffrey said, "ISIS is pitching this as a victory for them."

Trump and other administration officials have insisted his decision to pull back troops didn't constitute a green light to Ankara, which saw the US-allied Kurds as an extension of a terrorist group it considers an existential threat.

But on Wednesday, for a second day, lawmakers repeatedly returned to the question, with some noting that the US had spent the previous weeks convincing the Kurds to dismantle their defensive positions along the Turkish border.

Rep. Adam Kinzinger, an Illinois Republican and military veteran, asked Jeffrey if Turkey had threatened to proceed even if the US didn't withdraw its troops. Jeffrey said Ankara never felt constrained because the American troops were not told to stand their ground.

"There was never a consideration in the Turkish decision chain about US forces being in the way or anything else, because they never felt they were being blocked by the US forces," Jeffrey said. On Tuesday, Jeffrey had told the Senate Foreign Relations Committee that, "if US troops had been given the order to stand and fight against a NATO ally, I think you're right, the Turks may have thought twice. They have never been given that order."

While some of Trump's claims were undermined or refuted by his on-the-ground expert, the President also contradicted himself. Trump said Wednesday that America was "getting out" of the Middle East, yet earlier this month, he announced the US would send up to 3,000 additional troops to Saudi Arabia, which would pay for them.

At other times, he made broadly inaccurate claims, saying, "American forces defeated 100% of the ISIS Caliphate over the last two years." In fact, the US worked with a global coalition, founded in 2014, that is now made up of around 80 countries, and Kurdish troops did most of the fighting for the US.

Trump, on Wednesday, claimed, "Turkey, Syria and all forms of the Kurds have been fighting for centuries. We have done them a great service and we have done a great job... and now we're getting out."

But lawmakers in both parties have been vociferous in criticizing the President's decision, saying it has undermined the fight against ISIS, damaged the US ability to form future alliances, reduced US influence in the region and handed Russia and Iran a victory by giving them more sway over the Middle East.

Erdogan and Russian President Vladimir Putin met Tuesday to cement an agreement on joint Russian-Turkish patrols along much of the border with Syria and demand the Kurds withdraw their fighters and weapons from the area.

Adeline Van Houtte, a Europe analyst at the Economist Intelligence Unit, said the situation was "a fabulous win for Putin," who has now reinforced his status as the main powerbroker in Syria, gained control over an area previously occupied by US troops, increased Turkish dependence on Moscow and positioned his troops on a NATO border.

"Driving a wedge between NATO members is yet another key goal for Russia," Van Houtte noted.

Anger on Capitol Hill

Sen. Marco Rubio, a Florida Republican, pointed out that Trump's decision undermines all three of the administration's stated goals in Syria -- preventing an ISIS resurgence, gaining US leverage in any political solution in Syria and pushing for the withdrawal of all Iranian forces.

As senators grilled Jeffery on Tuesday, they raised the prospect that a strengthened Iran presents an increased the threat to Israel. Others spoke of the sense of shame members of the US military feel about abandoning Kurdish fighters, while Sen. Ted Cruz, a Texas Republican, raised the possibility of a "genocide" against Kurds.

Jeffrey told lawmakers that the US was looking into one allegation that Turkey had used chemical weapons. "White phosphorous, which under some circumstances is a legitimate military ordnance, under other circumstances, it is not, you have to look at the circumstances and that's what we're doing now," Jeffrey said.

The envoy used the formal term when a country seeks information from another nation or lodges a protest, telling lawmakers that the US had "sent a high-level demarche to Ankara demanding an explanation and we'll look at the various options."

Sen. Tim Kaine, a Virginia Democrat, noted that 176,000 Kurds had been displaced since the Turkish incursion, half of them children.

In a signal of the potential blowback the President could experience for his stance on Turkey, Senate Majority Leader Mitch McConnell said Tuesday that he would introduce a resolution urging Trump to end the troop drawdown, citing the "grave consequences of US withdrawal."

McConnell's resolution condemns the Turkish invasion into Syria, recognizes the Kurds for their role in fighting for the US against ISIS and asks Trump to rethink his invitation to Erdogan to visit Washington.

But on Wednesday, Trump announced that he and the Turkish leader "may be meeting in the very near future" and stressed what a "very good relationship" he has with Erdogan. He also admitted that it was "somewhat questionable" the ceasefire would remain permanent.

Turkish foreign minister Mevlut Cavusoglu said Wednesday that Turkey had stopped operations in northeastern Syria, but if troops come "face to face with any terrorist elements, if there are any remaining who have not withdrawn, we will neutralize them."

The President's move to ease sanctions and possibly go forward with an invitation to Erdogan will likely deepen anger on Capitol Hill, where lawmakers are questioning whether Turkey, a NATO ally, is becoming more of a foe. They point to Ankara's track record -- attacking US allies, buying Russian weapons systems, jailing Americans, including consular employees, and its steady march away from democracy toward a more authoritarian system.

Trump's decision to lift sanctions that were already seen as largely toothless could deepen frustrations among lawmakers angered by the President's refusal to impose legally required sanctions on Turkey for its purchase of the S400 missile defense system.

Van Houtte said Trump's moves give Turkey "another victory," as the "US sanctions on Turkey were weak and have now been lifted, making Turkey's life even easier."

The decision could also renew questions about Trump's affinity for Erdogan. On Tuesday, Jeffrey and Deputy Assistant Secretary of State for European and Eurasian Affairs Matthew Palmer were both asked if anyone had discussed the Trump Organization's business interests in Turkey with them. They both said no.