WASHINGTON, Feb 26, 2015 (BSS/AFP) - US Secretary of State John Kerry on Wednesday accused Russian President Vladimir Putin of destabilizing Ukraine through "land grabs," warning Moscow and the rebels had failed to meet the terms of a tattered ceasefire.

Putin had put in place policies which "violate all the international norms with respect to territory and behavior," Kerry told lawmakers.

"In Luhansk, and Donetsk, and now in Debaltseve, he has empowered, encouraged, and facilitated directly land grabs in order to try to destabilize Ukraine itself."

For a long time "the respect for international boundaries, and lines, and not taking territory by force, and subterfuge has been the standard for which nations have been trying to fight," Kerry told the House foreign affairs committee on Wednesday.

Top US officials have lashed Putin and his ministers in recent days as the fighting has continued in Ukraine, with Kerry on Tuesday directly accusing Russian leaders of lying "to my face" over the conflict.

"To date, neither Russia nor the forces it is supporting have come close to complying with their commitments," Kerry said Wednesday in a prepared statement to lawmakers on the second day of intense congressional hearings.

And he renewed warnings that "if failure continues, there will be further consequences -- consequences that would place added strains on Russia's weakened economy."

- 'How dumb do I look?' -

Asked if she believed Putin's assertions that he wanted peace in Ukraine, National Security Advisor Susan Rice retorted: "How dumb do I look?"

"No. In all seriousness, no. One cannot accept Vladimir Putin at his word because his actions have belied his words repeatedly, particularly in the context of Ukraine," Rice told PBS television.

Highlighting the biting sanctions which have already had a damaging effect on the Russian economy, Rice said that "how much he cares is a bigger question. I think he has to care."

"Will that, in the short term, cause him to -- to take the steps that we think are critical for him to take? That's a question to be answered. But this will come at a mounting and painful cost to the Russian economy and to Russian interests, particularly if he continues down this path."

NATO's top commander for Europe, Philip Breedlove, echoed her concerns, saying Putin has moved in a lot of force.

"Over a thousand combat vehicles, Russian combat forces, some of their most sophisticated air defense, battalions of artillery, Mr Putin has already set the bar ... very high in his interactions in Eastern Ukraine and in Donbass," he said in Washington.

"The disinformation campaign that Russia has out is quite pervasive," he argued.

But "what is clear is that right now it is not getting better; it is getting worse every day," Breedlove added.

For the first time since the European-brokered truce came into force on February 15, no deaths were reported in Ukraine's war zone by either side for the past 24 hours.

But there was still no confirmation, from the Organization for Security and Cooperation in Europe (OSCE), of a pull-back of heavy weapons from the frontline -- the other key plank of the truce.