Daleep Singh, the White House's top national security official crafting sanctions, spoke to reporters about the administration's sanctions against Russians and hinted that this is only the beginning of the United States' plan to defend Ukraine.

"If Putin escalates further, we will escalate further, using financial sanctions and export controls," Singh said.

Singh claimed the sanctions will only hurt the Russian economy.

"None of our measures are designed to disrupt the flow of energy to global markets. And we are now executing a plan in coordination with major oil producers and major oil consumers to secure the stability of global energy supplies," he said.

When asked by ABC News’ Cecilia Vega what it will take to target Putin personally, Singh said he wouldn’t say “exactly what it would take” but added that “no option is off the table.”

-ABC News' Ben Gittleson

Ukrainian President Volodymyr Zelenskyy signed a decree calling up some of Ukraine's military reservists but said a full mobilization of the country’s military is not needed for now.

Zelenskyy announced his plan on state TV, adding that the soldiers were from the “active reserve” and have military experience.

“They must heighten the readiness of the Ukrainian army for all possible changes in the active situation,” Zelenskyy said.

-ABC News' Patrick Reevell

Secretary of State Antony Blinken, in a joint appearance from the State Department with Ukrainian Foreign Minister Dmytro Kuleba, announced that he would not attend a meeting with his Russian counterpart on Thursday as planned.

"Now that we see the invasion is beginning, and Russia has made clear its wholesale rejection of diplomacy, it does not make sense to go forward with that meeting at this time," Blinken said Tuesday. "I consulted with our allies and partners. All agreed. And today I sent Foreign Minister Lavrov a letter informing him of this."

Blinken had agreed last week to meet with Russian Foreign Minister Sergei Lavrov on Thursday, provided there was no invasion of Ukraine, but called Putin’s recent comments “deeply disturbing” and placed aggression in the region squarely on Russia despite the Kremlin’s claims.

"Any further escalatory steps by Russia will be met with further swift and severe measures, coordinated with allies and partners," Blinken added, echoing remarks from Biden.

After meeting earlier with Secretary of Defense Lloyd Austin and ahead of his appearance with Blinken, Kuleba went to the White House to meet with Biden where the president updated him on the U.S. response, including the new sanctions, and reaffirmed U.S. security and economic assistance will continue, according to the White House.

The U.S. Treasury Department has released details of the new sanctions that President Joe Biden announced, including the specific elites who are sanctioned and more details about limits on Russian financial institutions.

A senior Biden administration official told reporters on an afternoon call that while "these are severe costs that we're imposing today," the U.S. was choosing to hold off with more severe sanctions as leverage to try to deter a wider-scale invasion of Ukraine.

The official also said "none of the sanctions are designed to disrupt the flow of energy to global markets" and noted the administration deliberately tried to make sure the pain was felt by Russia's economy, not by the U.S.

The Treasury Department release detailed that it was sanctioning five "Kremlin-connected elites" and two Russian state-owned financial institutions, as well as putting more restrictions on Russian sovereign debt.

The administration official said "sanctions are meant to serve a higher purpose," which they said was to "prevent a large scale invasion of Ukraine that involves the seizure of major cities including Kyiv" as well as "to prevent largescale human suffering" and "to prevent Putin from installing a puppet government that bends to his wishes and denies Ukraine the freedom to set its own course and choose its own destiny."

Asked by ABC News' Chief Washington Correspondent Jonathan Karl about sanctioning Putin, the official said that "all options remain on the table."

-ABC News' Ben Gittleson