Western powers are to attempt to inject diplomatic momentum behind the military strikes against Syrian government chemical weapon sites by calling for the UN to launch a broad investigation into Syria’s chemical weapons stockpiles.

The aim is to show that the western military intervention is part of a wider political and diplomatic strategy to drive chemical weapons from Syria once and for all.

A draft resolution will call on the whole of the UN to try to reinvigorate the stalled peace talks, accept a ceasefire and restore humanitarian access to besieged areas.

The diplomatic initiative came as the US appeared to have decided to maintain a 2,000-strong US troop presence in Syria indefinitely.

The UN security council’s 15 members will meet on Monday to discuss the call for a wider push to eliminate the covert Syrian government stockpiles, placing pressure on Russia to stop protecting Bashar al-Assad’s regime from a UN inquiry into its use of chemical weapons.

The three allies, the US, UK and France, have produced a draft UN resolution that includes proposals for an independent investigation into alleged toxic gas attacks in Syria to identify perpetrators. The Organisation for the Prohibition of Chemical Weapons (OPCW) would be instructed to report within 30 days whether Assad’s government had fully disclosed its chemical weapons stockpile.

The security council has been deadlocked since November over establishing an investigatory mechanism to identify responsibility for a chemical attacks, as opposed to determining whether an attack has occurred.

The draft resolution calls for medical evacuations and the safe passage for aid convoys to all areas of Syria. A ceasefire resolution that was adopted in February but never materialised should also be enforced, it adds.

The document “demands” that the Assad regime engage in peace talks “in good faith, constructively and without pre-conditions”.

The western initiative at the UN came as the US envoy to the UN, Nikki Haley, said US troops – numbering about 2,000 – would be staying in Syria until their mission was complete. Last month, Trump surprised his military by announcing they would be coming home soon.

Haley told Fox News the troops would stay until Islamic State was defeated, Syria’s chemical weapons stockpile could not be used to harm US interests, and until there was a good vantage point to watch what Iran was doing inside Syria. “We are not going to leave until we have accomplished those things,” she said.

She announced fresh US sanctions would be applied on Monday against companies linked to the use of chemical weapons by the Syrian government.

She summed up the crisis by saying: “Assad knew that Russia had its back, Assad knew that Russia would cover for them at the United Nations, and Assad got reckless, and he used it in a way that was far more aggressive. We have to be conscious of the fact that we can’t allow even the smallest use of chemical weapons.” Haley has claimed Syria has used chemical weapons 50 times since the civil war started eight years ago.

France in particular wants to follow up the air strikes with a fresh effort to examine if Russia recognises it must restrain the methods of a reckless Assad leadership. Syria’s air force was contining with air raids on Sunday using conventional weapons.

The OPCW is in Damascus to certify whether a chemical attack occurred on 7 April, which prompted Saturday’s airstrikes, but it has no wider terms of reference.

EU foreign minsters are expected to back the call at a meeting on Monday in Brussels. The proposal is also likely to be discussed at an Arab League summit hosted by Saudi Arabia.

The French foreign minister, Jean-Yves Le Drian, called for urgent action to avoid a further humanitarian disaster by forestalling an expected Syrian assault on the last major opposition-held province of Idlib in north-eastern Syria. Le Drian called for the jihadist groups that dominate the area to be disarmed and for Russia to order Syria to hold back from further assaults. He said Russia “should join our efforts to promote a political process in Syria that would allow a way out of the crisis”.

The UK foreign secretary, Boris Johnson, said on Sunday it would be “an extra” if the airstrikes led to Russia putting pressure on Assad to negotiate, but he said the action had been designed to deter and degrade Syria’s ability to use chemical weapons rather than change the course of the civil war.

Russia and Syria both continued to denounce the air assault as an illegal act of aggression. But Russia has failed to lever any major European country into opposing the strikes; at an emergency security council meeting on Saturday, only three countries backed a Russian resolution denouncing the airstrikes as an illegal act of aggression.

Vladimir Putin said in a phone call with his Iranian counterpart, Hassan Rouhani on Sunday: “If such actions, carried out in violation of the United Nations charter, are repeated, that would inevitably provoke chaos in international relations.”

The two leaders found “this illegal action seriously damaged the prospects of a political settlement in Syria,” the Kremlin said.

Haley told the security council on Saturday that US forces were “ready, locked and loaded” to mount further strikes if there were signs that Assad was planning to use chemical weapons again.

The narrowly targeted pre-dawn military operation on Saturday took aim at three alleged chemical weapons facilities. The allies believe they have a further set of targets established and a system of coordination in place that will prevent the delays in the assault that reduced the impact of Saturday morning’s strikes.