By John Irish

PARIS, Jan 6 (Reuters) - The United States for the first time on Tuesday backed a broad coalition of Ukraine's allies in vowing to provide security guarantees that leaders said would include binding commitments to support the country if it is attacked by Russia again.

The pledge came at a summit in Paris of the "coalition of the willing" of mainly European nations to firm up security guarantees to reassure Kyiv in the event of a ceasefire with Russia, which invaded its neighbour in 2014 and again at full scale in 2022.

U.S. special envoy Steve Witkoff said after the summit that President Donald Trump "strongly stands behind security protocols".

"Those security protocols are meant to ... deter any attacks, any further attacks in Ukraine, and ... if there are any attacks, they're meant to defend, and they will do both. They are as strong as anyone has ever seen."

A statement by coalition leaders also said that allies will participate in a proposed U.S.-led ceasefire monitoring and verification mechanism.

Talks to bring the almost four-year conflict to an end have accelerated since November. However, Moscow has yet to signal willingness to make concessions after Kyiv pushed for changes to a U.S. proposal that initially backed Russia's main demands.

BRINGING GUARANTEES

The text approved by the coalition on Tuesday underscores how discussions on security guarantees have advanced in recent weeks, even though Moscow has given no public sign that it would accept such arrangements.

Until recently, much of the focus was on pledges of military aid for Ukraine's forces and possible contributions to an international reassurance force.

But attention has now shifted to legally binding guarantees to come to Kyiv's aid in the event of another attack by Moscow. The possibility of a military response is likely to trigger debate in many European countries, diplomats say.

"These commitments may include the use of military capabilities, intelligence and logistical support, diplomatic initiatives, adoption of additional sanctions," the leaders' statement said, adding that they would now "finalise binding commitments."

"We all want ... peace (in Ukraine) to be fair, lasting and clear-eyed… we want this peace to have its guarantees," French President Emmanuel Macron told a news conference after the summit.

EUROPE, US COOPERATION

European leaders present at the meeting, including Macron, British Prime Minister Keir Starmer, Polish Prime Minister Donald Tusk and Italy's Prime Minister Giorgia Meloni stressed that the statement showed renewed unity between Europe and the United States on helping Ukraine.

The leaders' statement also pledged a European-led "Multinational Force for Ukraine ... to support the rebuilding of Ukraine's armed forces and support deterrence" with "the proposed support of the US".

Kyiv has long said it cannot be safe without guarantees that are comparable to the NATO alliance's mutual defence agreement, to deter Russia from attacking again. Moscow wants any peace deal to bar Ukraine from military alliances.

(Additional reporting by Andrew Gray, Louise Rasmussen, Lili Bayer, Dominique Vidalon, Yuliia Dysa, Costas Pitas, Muvija M; Writing by John Irish and Ingrid Melander; Editing by Andrew Gray)