US State Secretary Antony Blinken on Wednesday arrived in Ukraine on an unannounced visit. He is expected to announce more than a billion dollars in fresh aid for Kiev as Washington continues upping its expenditure for Ukraine.

Blinken landed in Kiev as the government claims to have made some advances against Russia's forces in the east after struggling for months to gain any ground.

"We expect the secretary to be able to announce more than a billion dollars in new US funding for Ukraine during the course of this visit," a senior US State Department official said en route to Kiev.

Check out: How much aid has the US sent to Ukraine?

Blinken was greeted by US Ambassador Bridget Brink upon his arrival in the Ukrainian capital.

The visit comes at a time when Ukraine is changing its strategy on the battlefield, which the State Department official claimed was a "good time" for Blinken to come, months into Kiev's counter-offensive and as energy security fears are on the rise again.

Some reports claim that the Ukrainian counteroffensive has been moving along more quickly lately and achieved some notable victories. The White House's spokesperson, John Kirby, lauded the Ukrainian troops' "notable progress" during the previous 72 hours in a southern offensive near the Zaporizhzhia area after they allegedly took over the village of Robotyne last week. 

Read next: Ukraine’s counteroffensive is 'running back into stalemate': Reports

Oleksandr Tarnavskiy, a brigadier general in the Ukrainian army, claimed over the weekend that his nation's forces had successfully breached Russia's first defensive line near Zaporizhzhia and that Moscow had only devoted 20% of its time and resources to each of the second and third lines.

While the recent news seems to be in favor of Ukraine, it appears that its supporters are working on keeping expectations in check rather than boosting them.

Read: US expects Ukraine counteroffensive not to meet goals: WashPo

The counterattack by Ukraine has been moving slowly for a variety of reasons, not the least of which is the size of the task. Former British general Sir Richard Barrons pointed out that progress has been made in the south this summer, but there are still 55 miles to go before Ukraine reaches its much-touted aim of reaching the Sea of Azov and severing the land bridge to Crimea. 

The well-established and extensive network of Russian defenses, including minefields, anti-tank ditches, and "Dragon's Teeth" barricades, have also forced Ukrainian forces to engage in combat, UnHerd reported.

Oleksii Reznikov, the recently ousted defense minister of Ukraine, lamented the presence of up to five Russian mines per square meter of land. This has considerably slowed down Ukrainian forces' advancement; according to Tarnavskiy, minefields have been impeding Ukrainian forces for weeks as infantry sappers tried to clear an attack route on foot while Russian forces used drones and shells to target vehicles. 

That is prior to discussing difficulties with the availability of ammunition and training. The US won't begin training F-16 fighter jet pilots until October, and according to Troels Poulsen, the acting defense minister of Denmark, Ukraine won't see results until the beginning of next year. Ukrainian soldiers have reported crippling disconnects between NATO drills and the realities of the front lines, despite the fact that 63,000 of their soldiers have participated in training in NATO countries due to time constraints.

It is worth noting that despite the fact that Ukraine's counteroffensive is moving more slowly than anticipated, Ukraine continues to reject the option of freezing the battle.