Kyiv watched as Russians massed on the border, but they weren’t allowed to use long-range missiles provided by Washington.

Ukrainian officials are making a new push to get the Biden administration to lift its ban on using U.S.-made weapons to strike inside Russia, saying the policy kept them from attacking Russian positions as they prepared for their major march toward Kharkiv.

A group of Ukrainian parliamentarians is in Washington this week to enlist congressional help on the issue, which they see as handcuffing the Ukrainian war effort as Kyiv looks to hit Russian military supply depots over the border.

Just this week, tens of thousands of Russian troops poured over the border in Ukraine’s northeast in an assault that Ukrainian intelligence officials had been anticipating for months. The Russians are smashing into overstretched, equipment-hungry Ukrainian units that are giving up ground as they regroup.

Ukrainian officials watched for weeks as the Russians massed near the Ukrainian border, unable to use U.S.-supplied weapons to conduct a preemptive strike due to Washington’s policy. The Biden administration, as a condition of sending the long-range weapons to Ukraine, said they could not be used to strike inside Russian territory.

“The main problem right now is the White House policy to limit our capability” to strike military targets inside Russia, David Arakhamia, chair of the ruling Servant of the People party in the Ukrainian parliament, said during a visit to Washington on Tuesday.

Russia is well aware of this limitation, and was able to mass at least 30,000 troops and equipment on the border without fear of being hit by long-range U.S.-supplied Army Tactical Missile Systems, which Ukraine has used to devastating effect on Russian troops inside Ukraine.

“We saw their military sitting one or two kilometers from the border inside Russia and there was nothing we could do about that,” Oleksandra Ustinova, the head of Ukraine’s special parliamentary commission on arms and munitions, said in a separate interview.

Russia has since clawed back ground Ukraine took last year during its counteroffensive, which pushed Russian forces back across the border.

The parliamentarians are part of a larger group of Ukrainian lawmakers meeting with around a dozen congressional offices this week to attempt to enlist them in their push to get the White House to change course.

Two U.S. officials, when asked for comment, confirmed that the Biden administration’s policy has not changed. “The assistance is for the defense and not for offensive operations in Russian territory,” said one of the officials, who was granted anonymity to discuss sensitive issues.

The Russian assault is taking advantage of Ukraine’s manpower issues, and the lack of properly prepared defenses near Kharkiv, putting the city of 1 million residents at risk and potentially giving Russia a critical new foothold in the country.

Vladimir Putin said in March that he was considering establishing a buffer zone near Kharkiv to make it harder for Ukraine to launch small drones targeting Russian oil infrastructure, a tactic that Kyiv has been using for months to hit Moscow’s economy.

The Institute for the Study of War assessed Monday that Russian forces had already captured several towns near the border and are destroying bridges to make it more difficult for Ukraine to counterattack, moves which “suggest that Russian forces are prioritizing the creation of a ‘buffer zone’ over a deeper penetration.”

The Biden administration’s restriction on using U.S.-made weapons inside Russia has been in place since Russia’s full-scale invasion in February 2022, and has long frustrated Ukrainian officials.

The Russians are “smart now,” Ustinova said, “because they know there is a restriction for Ukrainians to shoot at the Russian territory. And we saw all of their military equipment sitting one or two kilometers from the border [near Kharkiv] and there was nothing we could do.”

The U.K. government this month lifted a similar restriction on the use of British weapons inside Russia, an announcement made by British Foreign Secretary David Cameron during a visit to Kyiv. “Just as Russia is striking inside Ukraine, you can quite understand why Ukraine feels the need to make sure it’s defending itself,” he said.

U.S. officials increasingly believe Putin’s plans to mobilize new military units, coupled with additional ammunition from Beijing and dwindling Western support for Kyiv, could land him a win in Ukraine — and sooner than expected.

It might not be the win that Putin originally wanted, which was a total takeover of Ukraine. But by the end of this year, he may be able to use his gains to negotiate favorable terms for Moscow, three officials familiar with Western intelligence say.

The analysis is significantly more severe than the one offered by American officials six months ago, and suggests that the lack of ammunition in Ukraine’s ranks and Russia’s strengthening position on the battlefield has changed the course of the war.

“The war is as much about sending a signal to Putin that he can’t march across Europe as it is about supporting Kyiv,” said one of the officials, who like others was granted anonymity to discuss intelligence. “Putin is getting the opposite message.”

The Russian leader has taken command of a new cadre of paramilitary fighters that will allow him to finance and resource a new mobilization this summer, the officials said.

Those fighters formerly employed by Wagner — the paramilitary force that was led by Yevgeny Prigozhin — have folded into new units that will be used to fortify Russia’s positions in Ukraine.

Those new troops will give Russia the ability to push toward Kharkiv, which has been increasingly pounded by Russian air and missile strikes in preparation for the ground assault. The new forces will also allow less experienced troops to hold the ground already captured, creating a bleak new reality for Kyiv as it struggles to recruit new troops.

Ukraine has for months launched strikes inside Russia using its own small drones to attack oil facilities. But officials in Kyiv insist they need the more powerful U.S. missiles to break through Russian air defenses along the border.

“Everybody knew the Russians near Kharkiv [were] bringing the manpower, everybody knew they were bringing a lot of artillery, so what they’re aiming at doing now is they’re going to turn Kharkiv into the second Mariupol, or Aleppo,” Ustinova said.

“We keep coming back to the same problem — that it’s Russia telling us what we should be doing,” she said. “You’re giving us a stick but you will not let us use it.”