Russia’s move to rescind authority to invade Ukraine is welcome but is not enough to head off possible new European and U.S. economic sanctions, Secretary of State John F. Kerry said Wednesday.

The upper house of Russia’s parliament voted Wednesday to revoke invasion powers it had granted President Vladimir Putin on March 1. Putin had requested the move a day earlier, saying he wanted to help support Ukraine’s fledgling peace process by reducing tensions.

“That’s important. It’s a great step,” Kerry said after NATO meetings here. “But it could be reversed in 10 minutes, and everybody knows that.”

Kerry said that Russia must stop the flow of weapons and fighters across the border with Ukraine and that Putin should publicly call for pro-Russian separatists in eastern Ukraine to lay down arms. Russian forces and equipment should retreat from the border, he added, and Russia should use its influence to gain the release of monitors from the Organization for Security and Cooperation in Europe taken hostage by rebels in eastern Ukraine.

“Unless Russia fully makes that kind of commitment to the peace process and to the stability of Ukraine, the United States and Europe are compelled to continue to prepare greater costs, including tough economic sanctions, with the hopes that they will not have to be used,” Kerry said. “That is dependent on the choices that Russia and its president make in the next days and weeks.”

Russia has done nothing to comply with international demands to curtail its intervention in Ukraine, NATO’s chief said Wednesday.

“I regret to say that we see no signs that Russia is respecting its international commitments,” NATO Secretary General Anders Fogh Rasmussen told reporters during a meeting of alliance foreign ministers in Brussels.

NATO suspended cooperation with Russia in April in protest of its annexation of Ukraine’s Crimea region and is unlikely to reverse the decision soon.

British Foreign Secretary William Hague warned Wednesday that support for tougher European Union sanctions would increase if Russia fails to cooperate on Ukrainian President Petro Poroshenko’s peace plan.

Sectoral sanctions are “in the drawer” for use if needed and will be a subject of the E.U. meeting Friday, said a European diplomat, speaking on the condition of anonymity to describe behind-the-scenes efforts.

“The Americans are forcefully lobbying Europe in recent days not to relent on sanctions,” the diplomat said, acknowledging divisions within the E.U. about whether more sanctions are necessary now. “The jury is still out” on any decision this week, the diplomat added.

As he arrived for the NATO meetings, Hague said, “While there have been welcome words from Russia” about the peace plan, “we have not seen yet the actions to go with that.” He added, “We urge Russia to take the necessary action to stop the flow of arms across the border” and “stop supporting illegally armed separatist groups in eastern Ukraine, because in the absence of that action by Russia the case for stronger sanctions from European Union nations will, of course, become stronger.”

In an effort to spur sputtering peace talks, Poroshenko and Putin spoke Wednesday with German Chancellor Angela Merkel and French President François Hollande in a conference call. Poroshenko asked Russia to strengthen its border, his office said in a statement. He said he would be willing to allow Russian observers as part of a monitoring mission at the border during an ongoing but tenuous cease-fire. The leaders plan to speak again Thursday.

President Obama had called British Prime Minister David Cameron on Tuesday, and the White House said they had agreed that Russia must stop the flow of weapons and militants to separatists and encourage them to join the peace plan.

“Should Russia fail to take these immediate steps to deescalate the situation in eastern Ukraine, the United States and the European Union would work to implement additional coordinated measures to impose costs on Russia,” the White House said.

On Wednesday, Ukrainian Foreign Minister Pavlo Klimkin called Russia’s recision of invasion authority “a positive step” but said “mercenaries” and weapons continue to flow across the border. Ukrainian officials have said that the Kremlin is capable of destabilizing their country even without the war-powers authorization.

The cease-fire in eastern Ukraine, which both sides agreed to Monday, appeared to continue to be observed only partially Wednesday. Pro-Russian separatists a day earlier denounced the truce as a “sham,” saying that the Ukrainian military had not stopped fighting with them, and shot down a military helicopter, killing nine soldiers.

Klimkin said his nation remains committed to the peace plan but warned that the helicopter downing imperils it. It was the most serious breach of the cease-fire.

“We stick to our commitment” of a unilateral cease-fire and peace offer, Klimkin said after meetings with NATO officials and foreign ministers. “Such actions, such provocations, are extremely dangerous for getting the sustainable cease-fire and extremely dangerous for the peace plan.”

Kerry claimed the helicopter was shot down “with a Russian weapon.” Russia has repeatedly denied arming the rebels.

On Wednesday, a separatist leader, Pavel Gubarev, wrote on his Facebook page that rebel forces had destroyed an ammunition depot near the separatist-held city of Slovyansk.

Vice President Biden had called Poroshenko on Tuesday to offer condolences for the deaths aboard the Ukrainian transport helicopter. The White House said Biden “underscored the importance of having monitors in place to verify violations of the ceasefire, as well as the need to stop the supply of weapons and militants from across the border.”

Birnbaum in Kiev, Ukraine, and Karen DeYoung in Washington contributed to this report.